linux/mm/fadvise.c

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 14:07:57 +00:00
// SPDX-License-Identifier: GPL-2.0
/*
* mm/fadvise.c
*
* Copyright (C) 2002, Linus Torvalds
*
* 11Jan2003 Andrew Morton
* Initial version.
*/
#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/fadvise.h>
[PATCH] fadvise(): write commands Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:18:04 +00:00
#include <linux/writeback.h>
#include <linux/syscalls.h>
mm/fadvise.c: drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages Rob van der Heij reported the following (paraphrased) on private mail. The scenario is that I want to avoid backups to fill up the page cache and purge stuff that is more likely to be used again (this is with s390x Linux on z/VM, so I don't give it as much memory that we don't care anymore). So I have something with LD_PRELOAD that intercepts the close() call (from tar, in this case) and issues a posix_fadvise() just before closing the file. This mostly works, except for small files (less than 14 pages) that remains in page cache after the face. Unfortunately Rob has not had a chance to test this exact patch but the test program below should be reproducing the problem he described. The issue is the per-cpu pagevecs for LRU additions. If the pages are added by one CPU but fadvise() is called on another then the pages remain resident as the invalidate_mapping_pages() only drains the local pagevecs via its call to pagevec_release(). The user-visible effect is that a program that uses fadvise() properly is not obeyed. A possible fix for this is to put the necessary smarts into invalidate_mapping_pages() to globally drain the LRU pagevecs if a pagevec page could not be discarded. The downside with this is that an inode cache shrink would send a global IPI and memory pressure potentially causing global IPI storms is very undesirable. Instead, this patch adds a check during fadvise(POSIX_FADV_DONTNEED) to check if invalidate_mapping_pages() discarded all the requested pages. If a subset of pages are discarded it drains the LRU pagevecs and tries again. If the second attempt fails, it assumes it is due to the pages being mapped, locked or dirty and does not care. With this patch, an application using fadvise() correctly will be obeyed but there is a downside that a malicious application can force the kernel to send global IPIs and increase overhead. If accepted, I would like this to be considered as a -stable candidate. It's not an urgent issue but it's a system call that is not working as advertised which is weak. The following test program demonstrates the problem. It should never report that pages are still resident but will without this patch. It assumes that CPU 0 and 1 exist. int main() { int fd; int pagesize = getpagesize(); ssize_t written = 0, expected; char *buf; unsigned char *vec; int resident, i; cpu_set_t set; /* Prepare a buffer for writing */ expected = FILESIZE_PAGES * pagesize; buf = malloc(expected + 1); if (buf == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } buf[expected] = 0; memset(buf, 'a', expected); /* Prepare the mincore vec */ vec = malloc(FILESIZE_PAGES); if (vec == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } /* Bind ourselves to CPU 0 */ CPU_ZERO(&set); CPU_SET(0, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* open file, unlink and write buffer */ fd = open("fadvise-test-file", O_CREAT|O_EXCL|O_RDWR); if (fd == -1) { perror("open"); exit(EXIT_FAILURE); } unlink("fadvise-test-file"); while (written < expected) { ssize_t this_write; this_write = write(fd, buf + written, expected - written); if (this_write == -1) { perror("write"); exit(EXIT_FAILURE); } written += this_write; } free(buf); /* * Force ourselves to another CPU. If fadvise only flushes the local * CPUs pagevecs then the fadvise will fail to discard all file pages */ CPU_ZERO(&set); CPU_SET(1, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* sync and fadvise to discard the page cache */ fsync(fd); if (posix_fadvise(fd, 0, expected, POSIX_FADV_DONTNEED) == -1) { perror("posix_fadvise"); exit(EXIT_FAILURE); } /* map the file and use mincore to see which parts of it are resident */ buf = mmap(NULL, expected, PROT_READ, MAP_SHARED, fd, 0); if (buf == NULL) { perror("mmap"); exit(EXIT_FAILURE); } if (mincore(buf, expected, vec) == -1) { perror("mincore"); exit(EXIT_FAILURE); } /* Check residency */ for (i = 0, resident = 0; i < FILESIZE_PAGES; i++) { if (vec[i]) resident++; } if (resident != 0) { printf("Nr unexpected pages resident: %d\n", resident); exit(EXIT_FAILURE); } munmap(buf, expected); close(fd); free(vec); exit(EXIT_SUCCESS); } Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Rob van der Heij <rvdheij@gmail.com> Tested-by: Rob van der Heij <rvdheij@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23 00:35:59 +00:00
#include <linux/swap.h>
#include <asm/unistd.h>
/*
* POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
* deactivate the pages and clear PG_Referenced.
*/
int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
{
struct fd f = fdget(fd);
struct inode *inode;
struct address_space *mapping;
struct backing_dev_info *bdi;
[PATCH] fadvise(): write commands Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:18:04 +00:00
loff_t endbyte; /* inclusive */
pgoff_t start_index;
pgoff_t end_index;
unsigned long nrpages;
int ret = 0;
if (!f.file)
return -EBADF;
inode = file_inode(f.file);
if (S_ISFIFO(inode->i_mode)) {
ret = -ESPIPE;
goto out;
}
mapping = f.file->f_mapping;
if (!mapping || len < 0) {
ret = -EINVAL;
goto out;
}
mm: fadvise: avoid fadvise for fs without backing device The fadvise() manpage is silent on fadvise()'s effect on memory-based filesystems (shmem, hugetlbfs & ramfs) and pseudo file systems (procfs, sysfs, kernfs). The current implementaion of fadvise is mostly a noop for such filesystems except for FADV_DONTNEED which will trigger expensive remote LRU cache draining. This patch makes the noop of fadvise() on such file systems very explicit. However this change has two side effects for ramfs and one for tmpfs. First fadvise(FADV_DONTNEED) could remove the unmapped clean zero'ed pages of ramfs (allocated through read, readahead & read fault) and tmpfs (allocated through read fault). Also fadvise(FADV_WILLNEED) could create such clean zero'ed pages for ramfs. This change removes those possibilities. One of our generic libraries does fadvise(FADV_DONTNEED). Recently we observed high latency in fadvise() and noticed that the users have started using tmpfs files and the latency was due to expensive remote LRU cache draining. For normal tmpfs files (have data written on them), fadvise(FADV_DONTNEED) will always trigger the unneeded remote cache draining. Link: http://lkml.kernel.org/r/20170818011023.181465-1-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Greg Thelen <gthelen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08 23:13:05 +00:00
bdi = inode_to_bdi(mapping->host);
if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
check ADVICE of fadvise64_64 even if get_xip_page is given I've written some test programs in ltp project. During writing I met an problem which I cannot solve in user land. So I wrote a patch for linux kernel. Please, include this patch if acceptable. The test program tests the 4th parameter of fadvise64_64: long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice); My test case calls fadvise64_64 with invalid advice value and checks errno is set to EINVAL. About the advice parameter man page says: ... Permissible values for advice include: POSIX_FADV_NORMAL ... POSIX_FADV_SEQUENTIAL ... POSIX_FADV_RANDOM ... POSIX_FADV_NOREUSE ... POSIX_FADV_WILLNEED ... POSIX_FADV_DONTNEED ... ERRORS ... EINVAL An invalid value was specified for advice. However, I got a bug report that the system call invocations in my test case returned 0 unexpectedly. I've inspected the kernel code: asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) { struct file *file = fget(fd); struct address_space *mapping; struct backing_dev_info *bdi; loff_t endbyte; /* inclusive */ pgoff_t start_index; pgoff_t end_index; unsigned long nrpages; int ret = 0; if (!file) return -EBADF; if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) { ret = -ESPIPE; goto out; } mapping = file->f_mapping; if (!mapping || len < 0) { ret = -EINVAL; goto out; } if (mapping->a_ops->get_xip_page) /* no bad return value, but ignore advice */ goto out; ... out: fput(file); return ret; } I found the advice parameter is just ignored in the case mapping->a_ops->get_xip_page is given. This behavior is different from what is written on the man page. Is this o.k.? get_xip_page is given if CONFIG_EXT2_FS_XIP is true. Anyway I cannot find the easy way to detect get_xip_page field is given or CONFIG_EXT2_FS_XIP is true from the user space. I propose the following patch which checks the advice parameter even if get_xip_page is given. Signed-off-by: Masatake YAMATO <yamato@redhat.com> Acked-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 06:29:31 +00:00
switch (advice) {
case POSIX_FADV_NORMAL:
case POSIX_FADV_RANDOM:
case POSIX_FADV_SEQUENTIAL:
case POSIX_FADV_WILLNEED:
case POSIX_FADV_NOREUSE:
case POSIX_FADV_DONTNEED:
/* no bad return value, but ignore advice */
break;
default:
ret = -EINVAL;
}
goto out;
check ADVICE of fadvise64_64 even if get_xip_page is given I've written some test programs in ltp project. During writing I met an problem which I cannot solve in user land. So I wrote a patch for linux kernel. Please, include this patch if acceptable. The test program tests the 4th parameter of fadvise64_64: long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice); My test case calls fadvise64_64 with invalid advice value and checks errno is set to EINVAL. About the advice parameter man page says: ... Permissible values for advice include: POSIX_FADV_NORMAL ... POSIX_FADV_SEQUENTIAL ... POSIX_FADV_RANDOM ... POSIX_FADV_NOREUSE ... POSIX_FADV_WILLNEED ... POSIX_FADV_DONTNEED ... ERRORS ... EINVAL An invalid value was specified for advice. However, I got a bug report that the system call invocations in my test case returned 0 unexpectedly. I've inspected the kernel code: asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) { struct file *file = fget(fd); struct address_space *mapping; struct backing_dev_info *bdi; loff_t endbyte; /* inclusive */ pgoff_t start_index; pgoff_t end_index; unsigned long nrpages; int ret = 0; if (!file) return -EBADF; if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) { ret = -ESPIPE; goto out; } mapping = file->f_mapping; if (!mapping || len < 0) { ret = -EINVAL; goto out; } if (mapping->a_ops->get_xip_page) /* no bad return value, but ignore advice */ goto out; ... out: fput(file); return ret; } I found the advice parameter is just ignored in the case mapping->a_ops->get_xip_page is given. This behavior is different from what is written on the man page. Is this o.k.? get_xip_page is given if CONFIG_EXT2_FS_XIP is true. Anyway I cannot find the easy way to detect get_xip_page field is given or CONFIG_EXT2_FS_XIP is true from the user space. I propose the following patch which checks the advice parameter even if get_xip_page is given. Signed-off-by: Masatake YAMATO <yamato@redhat.com> Acked-by: Carsten Otte <cotte@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 06:29:31 +00:00
}
/* Careful about overflows. Len == 0 means "as much as possible" */
endbyte = offset + len;
if (!len || endbyte < len)
endbyte = -1;
[PATCH] fadvise(): write commands Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:18:04 +00:00
else
endbyte--; /* inclusive */
switch (advice) {
case POSIX_FADV_NORMAL:
f.file->f_ra.ra_pages = bdi->ra_pages;
spin_lock(&f.file->f_lock);
f.file->f_mode &= ~FMODE_RANDOM;
spin_unlock(&f.file->f_lock);
break;
case POSIX_FADV_RANDOM:
spin_lock(&f.file->f_lock);
f.file->f_mode |= FMODE_RANDOM;
spin_unlock(&f.file->f_lock);
break;
case POSIX_FADV_SEQUENTIAL:
f.file->f_ra.ra_pages = bdi->ra_pages * 2;
spin_lock(&f.file->f_lock);
f.file->f_mode &= ~FMODE_RANDOM;
spin_unlock(&f.file->f_lock);
break;
case POSIX_FADV_WILLNEED:
/* First and last PARTIAL page! */
mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-04-01 12:29:47 +00:00
start_index = offset >> PAGE_SHIFT;
end_index = endbyte >> PAGE_SHIFT;
/* Careful about overflow on the "+1" */
nrpages = end_index - start_index + 1;
if (!nrpages)
nrpages = ~0UL;
/*
* Ignore return value because fadvise() shall return
* success even if filesystem can't retrieve a hint,
*/
force_page_cache_readahead(mapping, f.file, start_index,
nrpages);
break;
case POSIX_FADV_NOREUSE:
break;
case POSIX_FADV_DONTNEED:
if (!inode_write_congested(mapping->host))
__filemap_fdatawrite_range(mapping, offset, endbyte,
WB_SYNC_NONE);
/*
* First and last FULL page! Partial pages are deliberately
* preserved on the expectation that it is better to preserve
* needed memory than to discard unneeded memory.
*/
mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-04-01 12:29:47 +00:00
start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
end_index = (endbyte >> PAGE_SHIFT);
mm/fadvise: discard partial page if endbyte is also EOF During our recent testing with fadvise(FADV_DONTNEED), we find that if given offset/length is not page-aligned, the last page will not be discarded. The tool we use is vmtouch (https://hoytech.com/vmtouch/), we map a 10KB-sized file into memory and then try to run this tool to evict the whole file mapping, but the last single page always remains staying in the memory: $./vmtouch -e test_10K Files: 1 Directories: 0 Evicted Pages: 3 (12K) Elapsed: 2.1e-05 seconds $./vmtouch test_10K Files: 1 Directories: 0 Resident Pages: 1/3 4K/12K 33.3% Elapsed: 5.5e-05 seconds However when we test with an older kernel, say 3.10, this problem is gone. So we wonder if this is a regression: $./vmtouch -e test_10K Files: 1 Directories: 0 Evicted Pages: 3 (12K) Elapsed: 8.2e-05 seconds $./vmtouch test_10K Files: 1 Directories: 0 Resident Pages: 0/3 0/12K 0% <-- partial page also discarded Elapsed: 5e-05 seconds After digging a little bit into this problem, we find it seems not a regression. Not discarding partial page is likely to be on purpose according to commit 441c228f817f ("mm: fadvise: document the fadvise(FADV_DONTNEED) behaviour for partial pages") written by Mel Gorman. He explained why partial pages should be preserved instead of being discarded when using fadvise(FADV_DONTNEED). However, the interesting part is that the actual code did NOT work as the same as it was described, the partial page was still discarded anyway, due to a calculation mistake of `end_index' passed to invalidate_mapping_pages(). This mistake has not been fixed until recently, that's why we fail to reproduce our problem in old kernels. The fix is done in commit 18aba41cbf ("mm/fadvise.c: do not discard partial pages with POSIX_FADV_DONTNEED") by Oleg Drokin. Back to the original testing, our problem becomes that there is a special case that, if the page-unaligned `endbyte' is also the end of file, it is not necessary at all to preserve the last partial page, as we all know no one else will use the rest of it. It should be safe enough if we just discard the whole page. So we add an EOF check in this patch. We also find a poosbile real world issue in mainline kernel. Assume such scenario: A userspace backup application want to backup a huge amount of small files (<4k) at once, the developer might (I guess) want to use fadvise(FADV_DONTNEED) to save memory. However, FADV_DONTNEED won't really happen since the only page mapped is a partial page, and kernel will preserve it. Our patch also fixes this problem, since we know the endbyte is EOF, so we discard it. Here is a simple reproducer to reproduce and verify each scenario we described above: test_fadvise.c ============================== #include <sys/mman.h> #include <sys/stat.h> #include <fcntl.h> #include <stdlib.h> #include <string.h> #include <stdio.h> #include <unistd.h> int main(int argc, char **argv) { int i, fd, ret, len; struct stat buf; void *addr; unsigned char *vec; char *strbuf; ssize_t pagesize = getpagesize(); ssize_t filesize; fd = open(argv[1], O_RDWR|O_CREAT, S_IRUSR|S_IWUSR); if (fd < 0) return -1; filesize = strtoul(argv[2], NULL, 10); strbuf = malloc(filesize); memset(strbuf, 42, filesize); write(fd, strbuf, filesize); free(strbuf); fsync(fd); len = (filesize + pagesize - 1) / pagesize; printf("length of pages: %d\n", len); addr = mmap(NULL, filesize, PROT_READ, MAP_SHARED, fd, 0); if (addr == MAP_FAILED) return -1; ret = posix_fadvise(fd, 0, filesize, POSIX_FADV_DONTNEED); if (ret < 0) return -1; vec = malloc(len); ret = mincore(addr, filesize, (void *)vec); if (ret < 0) return -1; for (i = 0; i < len; i++) printf("pages[%d]: %x\n", i, vec[i] & 0x1); free(vec); close(fd); return 0; } ============================== Test 1: running on kernel with commit 18aba41cbf reverted: [root@caspar ~]# uname -r 4.15.0-rc6.revert+ [root@caspar ~]# ./test_fadvise file1 1024 length of pages: 1 pages[0]: 0 # <-- partial page discarded [root@caspar ~]# ./test_fadvise file2 8192 length of pages: 2 pages[0]: 0 pages[1]: 0 [root@caspar ~]# ./test_fadvise file3 10240 length of pages: 3 pages[0]: 0 pages[1]: 0 pages[2]: 0 # <-- partial page discarded Test 2: running on mainline kernel: [root@caspar ~]# uname -r 4.15.0-rc6+ [root@caspar ~]# ./test_fadvise test1 1024 length of pages: 1 pages[0]: 1 # <-- partial and the only page not discarded [root@caspar ~]# ./test_fadvise test2 8192 length of pages: 2 pages[0]: 0 pages[1]: 0 [root@caspar ~]# ./test_fadvise test3 10240 length of pages: 3 pages[0]: 0 pages[1]: 0 pages[2]: 1 # <-- partial page not discarded Test 3: running on kernel with this patch: [root@caspar ~]# uname -r 4.15.0-rc6.patched+ [root@caspar ~]# ./test_fadvise test1 1024 length of pages: 1 pages[0]: 0 # <-- partial page and EOF, discarded [root@caspar ~]# ./test_fadvise test2 8192 length of pages: 2 pages[0]: 0 pages[1]: 0 [root@caspar ~]# ./test_fadvise test3 10240 length of pages: 3 pages[0]: 0 pages[1]: 0 pages[2]: 0 # <-- partial page and EOF, discarded [akpm@linux-foundation.org: tweak code comment] Link: http://lkml.kernel.org/r/5222da9ee20e1695eaabb69f631f200d6e6b8876.1515132470.git.jinli.zjl@alibaba-inc.com Signed-off-by: shidao.ytt <shidao.ytt@alibaba-inc.com> Signed-off-by: Caspar Zhang <jinli.zjl@alibaba-inc.com> Reviewed-by: Oliver Yang <zhiche.yy@alibaba-inc.com> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-01 00:19:55 +00:00
/*
* The page at end_index will be inclusively discarded according
* by invalidate_mapping_pages(), so subtracting 1 from
* end_index means we will skip the last page. But if endbyte
* is page aligned or is at the end of file, we should not skip
* that page - discarding the last page is safe enough.
*/
if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
endbyte != inode->i_size - 1) {
/* First page is tricky as 0 - 1 = -1, but pgoff_t
* is unsigned, so the end_index >= start_index
* check below would be true and we'll discard the whole
* file cache which is not what was asked.
*/
if (end_index == 0)
break;
end_index--;
}
mm/fadvise.c: drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages Rob van der Heij reported the following (paraphrased) on private mail. The scenario is that I want to avoid backups to fill up the page cache and purge stuff that is more likely to be used again (this is with s390x Linux on z/VM, so I don't give it as much memory that we don't care anymore). So I have something with LD_PRELOAD that intercepts the close() call (from tar, in this case) and issues a posix_fadvise() just before closing the file. This mostly works, except for small files (less than 14 pages) that remains in page cache after the face. Unfortunately Rob has not had a chance to test this exact patch but the test program below should be reproducing the problem he described. The issue is the per-cpu pagevecs for LRU additions. If the pages are added by one CPU but fadvise() is called on another then the pages remain resident as the invalidate_mapping_pages() only drains the local pagevecs via its call to pagevec_release(). The user-visible effect is that a program that uses fadvise() properly is not obeyed. A possible fix for this is to put the necessary smarts into invalidate_mapping_pages() to globally drain the LRU pagevecs if a pagevec page could not be discarded. The downside with this is that an inode cache shrink would send a global IPI and memory pressure potentially causing global IPI storms is very undesirable. Instead, this patch adds a check during fadvise(POSIX_FADV_DONTNEED) to check if invalidate_mapping_pages() discarded all the requested pages. If a subset of pages are discarded it drains the LRU pagevecs and tries again. If the second attempt fails, it assumes it is due to the pages being mapped, locked or dirty and does not care. With this patch, an application using fadvise() correctly will be obeyed but there is a downside that a malicious application can force the kernel to send global IPIs and increase overhead. If accepted, I would like this to be considered as a -stable candidate. It's not an urgent issue but it's a system call that is not working as advertised which is weak. The following test program demonstrates the problem. It should never report that pages are still resident but will without this patch. It assumes that CPU 0 and 1 exist. int main() { int fd; int pagesize = getpagesize(); ssize_t written = 0, expected; char *buf; unsigned char *vec; int resident, i; cpu_set_t set; /* Prepare a buffer for writing */ expected = FILESIZE_PAGES * pagesize; buf = malloc(expected + 1); if (buf == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } buf[expected] = 0; memset(buf, 'a', expected); /* Prepare the mincore vec */ vec = malloc(FILESIZE_PAGES); if (vec == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } /* Bind ourselves to CPU 0 */ CPU_ZERO(&set); CPU_SET(0, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* open file, unlink and write buffer */ fd = open("fadvise-test-file", O_CREAT|O_EXCL|O_RDWR); if (fd == -1) { perror("open"); exit(EXIT_FAILURE); } unlink("fadvise-test-file"); while (written < expected) { ssize_t this_write; this_write = write(fd, buf + written, expected - written); if (this_write == -1) { perror("write"); exit(EXIT_FAILURE); } written += this_write; } free(buf); /* * Force ourselves to another CPU. If fadvise only flushes the local * CPUs pagevecs then the fadvise will fail to discard all file pages */ CPU_ZERO(&set); CPU_SET(1, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* sync and fadvise to discard the page cache */ fsync(fd); if (posix_fadvise(fd, 0, expected, POSIX_FADV_DONTNEED) == -1) { perror("posix_fadvise"); exit(EXIT_FAILURE); } /* map the file and use mincore to see which parts of it are resident */ buf = mmap(NULL, expected, PROT_READ, MAP_SHARED, fd, 0); if (buf == NULL) { perror("mmap"); exit(EXIT_FAILURE); } if (mincore(buf, expected, vec) == -1) { perror("mincore"); exit(EXIT_FAILURE); } /* Check residency */ for (i = 0, resident = 0; i < FILESIZE_PAGES; i++) { if (vec[i]) resident++; } if (resident != 0) { printf("Nr unexpected pages resident: %d\n", resident); exit(EXIT_FAILURE); } munmap(buf, expected); close(fd); free(vec); exit(EXIT_SUCCESS); } Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Rob van der Heij <rvdheij@gmail.com> Tested-by: Rob van der Heij <rvdheij@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23 00:35:59 +00:00
if (end_index >= start_index) {
mm: fadvise: avoid expensive remote LRU cache draining after FADV_DONTNEED When FADV_DONTNEED cannot drop all pages in the range, it observes that some pages might still be on per-cpu LRU caches after recent instantiation and so initiates remote calls to all CPUs to flush their local caches. However, in most cases, the fadvise happens from the same context that instantiated the pages, and any pre-LRU pages in the specified range are most likely sitting on the local CPU's LRU cache, and so in many cases this results in unnecessary remote calls, which, in a loaded system, can hold up the fadvise() call significantly. [ I didn't record it in the extreme case we observed at Facebook, unfortunately. We had a slow-to-respond system and noticed it lru_add_drain_all() leading the profile during fadvise calls. This patch came out of thinking about the code and how we commonly call FADV_DONTNEED. FWIW, I wrote a silly directory tree walker/searcher that recurses through /usr to read and FADV_DONTNEED each file it finds. On a 2 socket 40 ht machine, over 1% is spent in lru_add_drain_all(). With the patch, that cost is gone; the local drain cost shows at 0.09%. ] Try to avoid the remote call by flushing the local LRU cache before even attempting to invalidate anything. It's a cheap operation, and the local LRU cache is the most likely to hold any pre-LRU pages in the specified fadvise range. Link: http://lkml.kernel.org/r/20161214210017.GA1465@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-20 00:23:03 +00:00
unsigned long count;
/*
* It's common to FADV_DONTNEED right after
* the read or write that instantiates the
* pages, in which case there will be some
* sitting on the local LRU cache. Try to
* avoid the expensive remote drain and the
* second cache tree walk below by flushing
* them out right away.
*/
lru_add_drain();
count = invalidate_mapping_pages(mapping,
mm/fadvise.c: drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages Rob van der Heij reported the following (paraphrased) on private mail. The scenario is that I want to avoid backups to fill up the page cache and purge stuff that is more likely to be used again (this is with s390x Linux on z/VM, so I don't give it as much memory that we don't care anymore). So I have something with LD_PRELOAD that intercepts the close() call (from tar, in this case) and issues a posix_fadvise() just before closing the file. This mostly works, except for small files (less than 14 pages) that remains in page cache after the face. Unfortunately Rob has not had a chance to test this exact patch but the test program below should be reproducing the problem he described. The issue is the per-cpu pagevecs for LRU additions. If the pages are added by one CPU but fadvise() is called on another then the pages remain resident as the invalidate_mapping_pages() only drains the local pagevecs via its call to pagevec_release(). The user-visible effect is that a program that uses fadvise() properly is not obeyed. A possible fix for this is to put the necessary smarts into invalidate_mapping_pages() to globally drain the LRU pagevecs if a pagevec page could not be discarded. The downside with this is that an inode cache shrink would send a global IPI and memory pressure potentially causing global IPI storms is very undesirable. Instead, this patch adds a check during fadvise(POSIX_FADV_DONTNEED) to check if invalidate_mapping_pages() discarded all the requested pages. If a subset of pages are discarded it drains the LRU pagevecs and tries again. If the second attempt fails, it assumes it is due to the pages being mapped, locked or dirty and does not care. With this patch, an application using fadvise() correctly will be obeyed but there is a downside that a malicious application can force the kernel to send global IPIs and increase overhead. If accepted, I would like this to be considered as a -stable candidate. It's not an urgent issue but it's a system call that is not working as advertised which is weak. The following test program demonstrates the problem. It should never report that pages are still resident but will without this patch. It assumes that CPU 0 and 1 exist. int main() { int fd; int pagesize = getpagesize(); ssize_t written = 0, expected; char *buf; unsigned char *vec; int resident, i; cpu_set_t set; /* Prepare a buffer for writing */ expected = FILESIZE_PAGES * pagesize; buf = malloc(expected + 1); if (buf == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } buf[expected] = 0; memset(buf, 'a', expected); /* Prepare the mincore vec */ vec = malloc(FILESIZE_PAGES); if (vec == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } /* Bind ourselves to CPU 0 */ CPU_ZERO(&set); CPU_SET(0, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* open file, unlink and write buffer */ fd = open("fadvise-test-file", O_CREAT|O_EXCL|O_RDWR); if (fd == -1) { perror("open"); exit(EXIT_FAILURE); } unlink("fadvise-test-file"); while (written < expected) { ssize_t this_write; this_write = write(fd, buf + written, expected - written); if (this_write == -1) { perror("write"); exit(EXIT_FAILURE); } written += this_write; } free(buf); /* * Force ourselves to another CPU. If fadvise only flushes the local * CPUs pagevecs then the fadvise will fail to discard all file pages */ CPU_ZERO(&set); CPU_SET(1, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* sync and fadvise to discard the page cache */ fsync(fd); if (posix_fadvise(fd, 0, expected, POSIX_FADV_DONTNEED) == -1) { perror("posix_fadvise"); exit(EXIT_FAILURE); } /* map the file and use mincore to see which parts of it are resident */ buf = mmap(NULL, expected, PROT_READ, MAP_SHARED, fd, 0); if (buf == NULL) { perror("mmap"); exit(EXIT_FAILURE); } if (mincore(buf, expected, vec) == -1) { perror("mincore"); exit(EXIT_FAILURE); } /* Check residency */ for (i = 0, resident = 0; i < FILESIZE_PAGES; i++) { if (vec[i]) resident++; } if (resident != 0) { printf("Nr unexpected pages resident: %d\n", resident); exit(EXIT_FAILURE); } munmap(buf, expected); close(fd); free(vec); exit(EXIT_SUCCESS); } Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Rob van der Heij <rvdheij@gmail.com> Tested-by: Rob van der Heij <rvdheij@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23 00:35:59 +00:00
start_index, end_index);
/*
* If fewer pages were invalidated than expected then
* it is possible that some of the pages were on
* a per-cpu pagevec for a remote CPU. Drain all
* pagevecs and try again.
*/
if (count < (end_index - start_index + 1)) {
lru_add_drain_all();
invalidate_mapping_pages(mapping, start_index,
[PATCH] fadvise(): write commands Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:18:04 +00:00
end_index);
mm/fadvise.c: drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages Rob van der Heij reported the following (paraphrased) on private mail. The scenario is that I want to avoid backups to fill up the page cache and purge stuff that is more likely to be used again (this is with s390x Linux on z/VM, so I don't give it as much memory that we don't care anymore). So I have something with LD_PRELOAD that intercepts the close() call (from tar, in this case) and issues a posix_fadvise() just before closing the file. This mostly works, except for small files (less than 14 pages) that remains in page cache after the face. Unfortunately Rob has not had a chance to test this exact patch but the test program below should be reproducing the problem he described. The issue is the per-cpu pagevecs for LRU additions. If the pages are added by one CPU but fadvise() is called on another then the pages remain resident as the invalidate_mapping_pages() only drains the local pagevecs via its call to pagevec_release(). The user-visible effect is that a program that uses fadvise() properly is not obeyed. A possible fix for this is to put the necessary smarts into invalidate_mapping_pages() to globally drain the LRU pagevecs if a pagevec page could not be discarded. The downside with this is that an inode cache shrink would send a global IPI and memory pressure potentially causing global IPI storms is very undesirable. Instead, this patch adds a check during fadvise(POSIX_FADV_DONTNEED) to check if invalidate_mapping_pages() discarded all the requested pages. If a subset of pages are discarded it drains the LRU pagevecs and tries again. If the second attempt fails, it assumes it is due to the pages being mapped, locked or dirty and does not care. With this patch, an application using fadvise() correctly will be obeyed but there is a downside that a malicious application can force the kernel to send global IPIs and increase overhead. If accepted, I would like this to be considered as a -stable candidate. It's not an urgent issue but it's a system call that is not working as advertised which is weak. The following test program demonstrates the problem. It should never report that pages are still resident but will without this patch. It assumes that CPU 0 and 1 exist. int main() { int fd; int pagesize = getpagesize(); ssize_t written = 0, expected; char *buf; unsigned char *vec; int resident, i; cpu_set_t set; /* Prepare a buffer for writing */ expected = FILESIZE_PAGES * pagesize; buf = malloc(expected + 1); if (buf == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } buf[expected] = 0; memset(buf, 'a', expected); /* Prepare the mincore vec */ vec = malloc(FILESIZE_PAGES); if (vec == NULL) { printf("ENOMEM\n"); exit(EXIT_FAILURE); } /* Bind ourselves to CPU 0 */ CPU_ZERO(&set); CPU_SET(0, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* open file, unlink and write buffer */ fd = open("fadvise-test-file", O_CREAT|O_EXCL|O_RDWR); if (fd == -1) { perror("open"); exit(EXIT_FAILURE); } unlink("fadvise-test-file"); while (written < expected) { ssize_t this_write; this_write = write(fd, buf + written, expected - written); if (this_write == -1) { perror("write"); exit(EXIT_FAILURE); } written += this_write; } free(buf); /* * Force ourselves to another CPU. If fadvise only flushes the local * CPUs pagevecs then the fadvise will fail to discard all file pages */ CPU_ZERO(&set); CPU_SET(1, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) { perror("sched_setaffinity"); exit(EXIT_FAILURE); } /* sync and fadvise to discard the page cache */ fsync(fd); if (posix_fadvise(fd, 0, expected, POSIX_FADV_DONTNEED) == -1) { perror("posix_fadvise"); exit(EXIT_FAILURE); } /* map the file and use mincore to see which parts of it are resident */ buf = mmap(NULL, expected, PROT_READ, MAP_SHARED, fd, 0); if (buf == NULL) { perror("mmap"); exit(EXIT_FAILURE); } if (mincore(buf, expected, vec) == -1) { perror("mincore"); exit(EXIT_FAILURE); } /* Check residency */ for (i = 0, resident = 0; i < FILESIZE_PAGES; i++) { if (vec[i]) resident++; } if (resident != 0) { printf("Nr unexpected pages resident: %d\n", resident); exit(EXIT_FAILURE); } munmap(buf, expected); close(fd); free(vec); exit(EXIT_SUCCESS); } Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Rob van der Heij <rvdheij@gmail.com> Tested-by: Rob van der Heij <rvdheij@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-23 00:35:59 +00:00
}
}
[PATCH] fadvise(): write commands Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:18:04 +00:00
break;
default:
ret = -EINVAL;
}
out:
fdput(f);
return ret;
}
SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
{
return ksys_fadvise64_64(fd, offset, len, advice);
}
#ifdef __ARCH_WANT_SYS_FADVISE64
SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
{
return ksys_fadvise64_64(fd, offset, len, advice);
}
#endif