linux/fs/xfs/xfs_aops.c
Brian Foster aa6ee4ab69 xfs: eof trim writeback mapping as soon as it is cached
The cached writeback mapping is EOF trimmed to try and avoid races
between post-eof block management and writeback that result in
sending cached data to a stale location. The cached mapping is
currently trimmed on the validation check, which leaves a race
window between the time the mapping is cached and when it is trimmed
against the current inode size.

For example, if a new mapping is cached by delalloc conversion on a
blocksize == page size fs, we could cycle various locks, perform
memory allocations, etc.  in the writeback codepath before the
associated mapping is eventually trimmed to i_size. This leaves
enough time for a post-eof truncate and file append before the
cached mapping is trimmed. The former event essentially invalidates
a range of the cached mapping and the latter bumps the inode size
such the trim on the next writepage event won't trim all of the
invalid blocks. fstest generic/464 reproduces this scenario
occasionally and causes a lost writeback and stale delalloc blocks
warning on inode inactivation.

To work around this problem, trim the cached writeback mapping as
soon as it is cached in addition to on subsequent validation checks.
This is a minor tweak to tighten the race window as much as possible
until a proper invalidation mechanism is available.

Fixes: 40214d128e ("xfs: trim writepage mapping to within eof")
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2019-02-03 14:02:49 -08:00

1044 lines
30 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2005 Silicon Graphics, Inc.
* Copyright (c) 2016-2018 Christoph Hellwig.
* All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_alloc.h"
#include "xfs_error.h"
#include "xfs_iomap.h"
#include "xfs_trace.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
#include "xfs_reflink.h"
#include <linux/writeback.h>
/*
* structure owned by writepages passed to individual writepage calls
*/
struct xfs_writepage_ctx {
struct xfs_bmbt_irec imap;
unsigned int io_type;
unsigned int cow_seq;
struct xfs_ioend *ioend;
};
struct block_device *
xfs_find_bdev_for_inode(
struct inode *inode)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
if (XFS_IS_REALTIME_INODE(ip))
return mp->m_rtdev_targp->bt_bdev;
else
return mp->m_ddev_targp->bt_bdev;
}
struct dax_device *
xfs_find_daxdev_for_inode(
struct inode *inode)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
if (XFS_IS_REALTIME_INODE(ip))
return mp->m_rtdev_targp->bt_daxdev;
else
return mp->m_ddev_targp->bt_daxdev;
}
static void
xfs_finish_page_writeback(
struct inode *inode,
struct bio_vec *bvec,
int error)
{
struct iomap_page *iop = to_iomap_page(bvec->bv_page);
if (error) {
SetPageError(bvec->bv_page);
mapping_set_error(inode->i_mapping, -EIO);
}
ASSERT(iop || i_blocksize(inode) == PAGE_SIZE);
ASSERT(!iop || atomic_read(&iop->write_count) > 0);
if (!iop || atomic_dec_and_test(&iop->write_count))
end_page_writeback(bvec->bv_page);
}
/*
* We're now finished for good with this ioend structure. Update the page
* state, release holds on bios, and finally free up memory. Do not use the
* ioend after this.
*/
STATIC void
xfs_destroy_ioend(
struct xfs_ioend *ioend,
int error)
{
struct inode *inode = ioend->io_inode;
struct bio *bio = &ioend->io_inline_bio;
struct bio *last = ioend->io_bio, *next;
u64 start = bio->bi_iter.bi_sector;
bool quiet = bio_flagged(bio, BIO_QUIET);
for (bio = &ioend->io_inline_bio; bio; bio = next) {
struct bio_vec *bvec;
int i;
/*
* For the last bio, bi_private points to the ioend, so we
* need to explicitly end the iteration here.
*/
if (bio == last)
next = NULL;
else
next = bio->bi_private;
/* walk each page on bio, ending page IO on them */
bio_for_each_segment_all(bvec, bio, i)
xfs_finish_page_writeback(inode, bvec, error);
bio_put(bio);
}
if (unlikely(error && !quiet)) {
xfs_err_ratelimited(XFS_I(inode)->i_mount,
"writeback error on sector %llu", start);
}
}
/*
* Fast and loose check if this write could update the on-disk inode size.
*/
static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
{
return ioend->io_offset + ioend->io_size >
XFS_I(ioend->io_inode)->i_d.di_size;
}
STATIC int
xfs_setfilesize_trans_alloc(
struct xfs_ioend *ioend)
{
struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount;
struct xfs_trans *tp;
int error;
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0,
XFS_TRANS_NOFS, &tp);
if (error)
return error;
ioend->io_append_trans = tp;
/*
* We may pass freeze protection with a transaction. So tell lockdep
* we released it.
*/
__sb_writers_release(ioend->io_inode->i_sb, SB_FREEZE_FS);
/*
* We hand off the transaction to the completion thread now, so
* clear the flag here.
*/
current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
return 0;
}
/*
* Update on-disk file size now that data has been written to disk.
*/
STATIC int
__xfs_setfilesize(
struct xfs_inode *ip,
struct xfs_trans *tp,
xfs_off_t offset,
size_t size)
{
xfs_fsize_t isize;
xfs_ilock(ip, XFS_ILOCK_EXCL);
isize = xfs_new_eof(ip, offset + size);
if (!isize) {
xfs_iunlock(ip, XFS_ILOCK_EXCL);
xfs_trans_cancel(tp);
return 0;
}
trace_xfs_setfilesize(ip, offset, size);
ip->i_d.di_size = isize;
xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
return xfs_trans_commit(tp);
}
int
xfs_setfilesize(
struct xfs_inode *ip,
xfs_off_t offset,
size_t size)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_trans *tp;
int error;
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
if (error)
return error;
return __xfs_setfilesize(ip, tp, offset, size);
}
STATIC int
xfs_setfilesize_ioend(
struct xfs_ioend *ioend,
int error)
{
struct xfs_inode *ip = XFS_I(ioend->io_inode);
struct xfs_trans *tp = ioend->io_append_trans;
/*
* The transaction may have been allocated in the I/O submission thread,
* thus we need to mark ourselves as being in a transaction manually.
* Similarly for freeze protection.
*/
current_set_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
__sb_writers_acquired(VFS_I(ip)->i_sb, SB_FREEZE_FS);
/* we abort the update if there was an IO error */
if (error) {
xfs_trans_cancel(tp);
return error;
}
return __xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
}
/*
* IO write completion.
*/
STATIC void
xfs_end_io(
struct work_struct *work)
{
struct xfs_ioend *ioend =
container_of(work, struct xfs_ioend, io_work);
struct xfs_inode *ip = XFS_I(ioend->io_inode);
xfs_off_t offset = ioend->io_offset;
size_t size = ioend->io_size;
int error;
/*
* Just clean up the in-memory strutures if the fs has been shut down.
*/
if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
error = -EIO;
goto done;
}
/*
* Clean up any COW blocks on an I/O error.
*/
error = blk_status_to_errno(ioend->io_bio->bi_status);
if (unlikely(error)) {
switch (ioend->io_type) {
case XFS_IO_COW:
xfs_reflink_cancel_cow_range(ip, offset, size, true);
break;
}
goto done;
}
/*
* Success: commit the COW or unwritten blocks if needed.
*/
switch (ioend->io_type) {
case XFS_IO_COW:
error = xfs_reflink_end_cow(ip, offset, size);
break;
case XFS_IO_UNWRITTEN:
/* writeback should never update isize */
error = xfs_iomap_write_unwritten(ip, offset, size, false);
break;
default:
ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);
break;
}
done:
if (ioend->io_append_trans)
error = xfs_setfilesize_ioend(ioend, error);
xfs_destroy_ioend(ioend, error);
}
STATIC void
xfs_end_bio(
struct bio *bio)
{
struct xfs_ioend *ioend = bio->bi_private;
struct xfs_mount *mp = XFS_I(ioend->io_inode)->i_mount;
if (ioend->io_type == XFS_IO_UNWRITTEN || ioend->io_type == XFS_IO_COW)
queue_work(mp->m_unwritten_workqueue, &ioend->io_work);
else if (ioend->io_append_trans)
queue_work(mp->m_data_workqueue, &ioend->io_work);
else
xfs_destroy_ioend(ioend, blk_status_to_errno(bio->bi_status));
}
STATIC int
xfs_map_blocks(
struct xfs_writepage_ctx *wpc,
struct inode *inode,
loff_t offset)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
ssize_t count = i_blocksize(inode);
xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset), end_fsb;
xfs_fileoff_t cow_fsb = NULLFILEOFF;
struct xfs_bmbt_irec imap;
int whichfork = XFS_DATA_FORK;
struct xfs_iext_cursor icur;
bool imap_valid;
int error = 0;
/*
* We have to make sure the cached mapping is within EOF to protect
* against eofblocks trimming on file release leaving us with a stale
* mapping. Otherwise, a page for a subsequent file extending buffered
* write could get picked up by this writeback cycle and written to the
* wrong blocks.
*
* Note that what we really want here is a generic mapping invalidation
* mechanism to protect us from arbitrary extent modifying contexts, not
* just eofblocks.
*/
xfs_trim_extent_eof(&wpc->imap, ip);
/*
* COW fork blocks can overlap data fork blocks even if the blocks
* aren't shared. COW I/O always takes precedent, so we must always
* check for overlap on reflink inodes unless the mapping is already a
* COW one, or the COW fork hasn't changed from the last time we looked
* at it.
*
* It's safe to check the COW fork if_seq here without the ILOCK because
* we've indirectly protected against concurrent updates: writeback has
* the page locked, which prevents concurrent invalidations by reflink
* and directio and prevents concurrent buffered writes to the same
* page. Changes to if_seq always happen under i_lock, which protects
* against concurrent updates and provides a memory barrier on the way
* out that ensures that we always see the current value.
*/
imap_valid = offset_fsb >= wpc->imap.br_startoff &&
offset_fsb < wpc->imap.br_startoff + wpc->imap.br_blockcount;
if (imap_valid &&
(!xfs_inode_has_cow_data(ip) ||
wpc->io_type == XFS_IO_COW ||
wpc->cow_seq == READ_ONCE(ip->i_cowfp->if_seq)))
return 0;
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
/*
* If we don't have a valid map, now it's time to get a new one for this
* offset. This will convert delayed allocations (including COW ones)
* into real extents. If we return without a valid map, it means we
* landed in a hole and we skip the block.
*/
xfs_ilock(ip, XFS_ILOCK_SHARED);
ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
(ip->i_df.if_flags & XFS_IFEXTENTS));
ASSERT(offset <= mp->m_super->s_maxbytes);
if (offset > mp->m_super->s_maxbytes - count)
count = mp->m_super->s_maxbytes - offset;
end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
/*
* Check if this is offset is covered by a COW extents, and if yes use
* it directly instead of looking up anything in the data fork.
*/
if (xfs_inode_has_cow_data(ip) &&
xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap))
cow_fsb = imap.br_startoff;
if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
wpc->cow_seq = READ_ONCE(ip->i_cowfp->if_seq);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
/*
* Truncate can race with writeback since writeback doesn't
* take the iolock and truncate decreases the file size before
* it starts truncating the pages between new_size and old_size.
* Therefore, we can end up in the situation where writeback
* gets a CoW fork mapping but the truncate makes the mapping
* invalid and we end up in here trying to get a new mapping.
* bail out here so that we simply never get a valid mapping
* and so we drop the write altogether. The page truncation
* will kill the contents anyway.
*/
if (offset > i_size_read(inode)) {
wpc->io_type = XFS_IO_HOLE;
return 0;
}
whichfork = XFS_COW_FORK;
wpc->io_type = XFS_IO_COW;
goto allocate_blocks;
}
/*
* Map valid and no COW extent in the way? We're done.
*/
if (imap_valid) {
xfs_iunlock(ip, XFS_ILOCK_SHARED);
return 0;
}
/*
* If we don't have a valid map, now it's time to get a new one for this
* offset. This will convert delayed allocations (including COW ones)
* into real extents.
*/
if (!xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap))
imap.br_startoff = end_fsb; /* fake a hole past EOF */
xfs_iunlock(ip, XFS_ILOCK_SHARED);
if (imap.br_startoff > offset_fsb) {
/* landed in a hole or beyond EOF */
imap.br_blockcount = imap.br_startoff - offset_fsb;
imap.br_startoff = offset_fsb;
imap.br_startblock = HOLESTARTBLOCK;
wpc->io_type = XFS_IO_HOLE;
} else {
/*
* Truncate to the next COW extent if there is one. This is the
* only opportunity to do this because we can skip COW fork
* lookups for the subsequent blocks in the mapping; however,
* the requirement to treat the COW range separately remains.
*/
if (cow_fsb != NULLFILEOFF &&
cow_fsb < imap.br_startoff + imap.br_blockcount)
imap.br_blockcount = cow_fsb - imap.br_startoff;
if (isnullstartblock(imap.br_startblock)) {
/* got a delalloc extent */
wpc->io_type = XFS_IO_DELALLOC;
goto allocate_blocks;
}
if (imap.br_state == XFS_EXT_UNWRITTEN)
wpc->io_type = XFS_IO_UNWRITTEN;
else
wpc->io_type = XFS_IO_OVERWRITE;
}
wpc->imap = imap;
xfs_trim_extent_eof(&wpc->imap, ip);
trace_xfs_map_blocks_found(ip, offset, count, wpc->io_type, &imap);
return 0;
allocate_blocks:
error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap,
&wpc->cow_seq);
if (error)
return error;
ASSERT(whichfork == XFS_COW_FORK || cow_fsb == NULLFILEOFF ||
imap.br_startoff + imap.br_blockcount <= cow_fsb);
wpc->imap = imap;
xfs_trim_extent_eof(&wpc->imap, ip);
trace_xfs_map_blocks_alloc(ip, offset, count, wpc->io_type, &imap);
return 0;
}
/*
* Submit the bio for an ioend. We are passed an ioend with a bio attached to
* it, and we submit that bio. The ioend may be used for multiple bio
* submissions, so we only want to allocate an append transaction for the ioend
* once. In the case of multiple bio submission, each bio will take an IO
* reference to the ioend to ensure that the ioend completion is only done once
* all bios have been submitted and the ioend is really done.
*
* If @fail is non-zero, it means that we have a situation where some part of
* the submission process has failed after we have marked paged for writeback
* and unlocked them. In this situation, we need to fail the bio and ioend
* rather than submit it to IO. This typically only happens on a filesystem
* shutdown.
*/
STATIC int
xfs_submit_ioend(
struct writeback_control *wbc,
struct xfs_ioend *ioend,
int status)
{
/* Convert CoW extents to regular */
if (!status && ioend->io_type == XFS_IO_COW) {
/*
* Yuk. This can do memory allocation, but is not a
* transactional operation so everything is done in GFP_KERNEL
* context. That can deadlock, because we hold pages in
* writeback state and GFP_KERNEL allocations can block on them.
* Hence we must operate in nofs conditions here.
*/
unsigned nofs_flag;
nofs_flag = memalloc_nofs_save();
status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode),
ioend->io_offset, ioend->io_size);
memalloc_nofs_restore(nofs_flag);
}
/* Reserve log space if we might write beyond the on-disk inode size. */
if (!status &&
ioend->io_type != XFS_IO_UNWRITTEN &&
xfs_ioend_is_append(ioend) &&
!ioend->io_append_trans)
status = xfs_setfilesize_trans_alloc(ioend);
ioend->io_bio->bi_private = ioend;
ioend->io_bio->bi_end_io = xfs_end_bio;
ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
/*
* If we are failing the IO now, just mark the ioend with an
* error and finish it. This will run IO completion immediately
* as there is only one reference to the ioend at this point in
* time.
*/
if (status) {
ioend->io_bio->bi_status = errno_to_blk_status(status);
bio_endio(ioend->io_bio);
return status;
}
ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
submit_bio(ioend->io_bio);
return 0;
}
static struct xfs_ioend *
xfs_alloc_ioend(
struct inode *inode,
unsigned int type,
xfs_off_t offset,
struct block_device *bdev,
sector_t sector)
{
struct xfs_ioend *ioend;
struct bio *bio;
bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, &xfs_ioend_bioset);
bio_set_dev(bio, bdev);
bio->bi_iter.bi_sector = sector;
ioend = container_of(bio, struct xfs_ioend, io_inline_bio);
INIT_LIST_HEAD(&ioend->io_list);
ioend->io_type = type;
ioend->io_inode = inode;
ioend->io_size = 0;
ioend->io_offset = offset;
INIT_WORK(&ioend->io_work, xfs_end_io);
ioend->io_append_trans = NULL;
ioend->io_bio = bio;
return ioend;
}
/*
* Allocate a new bio, and chain the old bio to the new one.
*
* Note that we have to do perform the chaining in this unintuitive order
* so that the bi_private linkage is set up in the right direction for the
* traversal in xfs_destroy_ioend().
*/
static void
xfs_chain_bio(
struct xfs_ioend *ioend,
struct writeback_control *wbc,
struct block_device *bdev,
sector_t sector)
{
struct bio *new;
new = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);
bio_set_dev(new, bdev);
new->bi_iter.bi_sector = sector;
bio_chain(ioend->io_bio, new);
bio_get(ioend->io_bio); /* for xfs_destroy_ioend */
ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
submit_bio(ioend->io_bio);
ioend->io_bio = new;
}
/*
* Test to see if we have an existing ioend structure that we could append to
* first, otherwise finish off the current ioend and start another.
*/
STATIC void
xfs_add_to_ioend(
struct inode *inode,
xfs_off_t offset,
struct page *page,
struct iomap_page *iop,
struct xfs_writepage_ctx *wpc,
struct writeback_control *wbc,
struct list_head *iolist)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
struct block_device *bdev = xfs_find_bdev_for_inode(inode);
unsigned len = i_blocksize(inode);
unsigned poff = offset & (PAGE_SIZE - 1);
sector_t sector;
sector = xfs_fsb_to_db(ip, wpc->imap.br_startblock) +
((offset - XFS_FSB_TO_B(mp, wpc->imap.br_startoff)) >> 9);
if (!wpc->ioend || wpc->io_type != wpc->ioend->io_type ||
sector != bio_end_sector(wpc->ioend->io_bio) ||
offset != wpc->ioend->io_offset + wpc->ioend->io_size) {
if (wpc->ioend)
list_add(&wpc->ioend->io_list, iolist);
wpc->ioend = xfs_alloc_ioend(inode, wpc->io_type, offset,
bdev, sector);
}
if (!__bio_try_merge_page(wpc->ioend->io_bio, page, len, poff)) {
if (iop)
atomic_inc(&iop->write_count);
if (bio_full(wpc->ioend->io_bio))
xfs_chain_bio(wpc->ioend, wbc, bdev, sector);
__bio_add_page(wpc->ioend->io_bio, page, len, poff);
}
wpc->ioend->io_size += len;
}
STATIC void
xfs_vm_invalidatepage(
struct page *page,
unsigned int offset,
unsigned int length)
{
trace_xfs_invalidatepage(page->mapping->host, page, offset, length);
iomap_invalidatepage(page, offset, length);
}
/*
* If the page has delalloc blocks on it, we need to punch them out before we
* invalidate the page. If we don't, we leave a stale delalloc mapping on the
* inode that can trip up a later direct I/O read operation on the same region.
*
* We prevent this by truncating away the delalloc regions on the page. Because
* they are delalloc, we can do this without needing a transaction. Indeed - if
* we get ENOSPC errors, we have to be able to do this truncation without a
* transaction as there is no space left for block reservation (typically why we
* see a ENOSPC in writeback).
*/
STATIC void
xfs_aops_discard_page(
struct page *page)
{
struct inode *inode = page->mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
loff_t offset = page_offset(page);
xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, offset);
int error;
if (XFS_FORCED_SHUTDOWN(mp))
goto out_invalidate;
xfs_alert(mp,
"page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
page, ip->i_ino, offset);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
PAGE_SIZE / i_blocksize(inode));
if (error && !XFS_FORCED_SHUTDOWN(mp))
xfs_alert(mp, "page discard unable to remove delalloc mapping.");
out_invalidate:
xfs_vm_invalidatepage(page, 0, PAGE_SIZE);
}
/*
* We implement an immediate ioend submission policy here to avoid needing to
* chain multiple ioends and hence nest mempool allocations which can violate
* forward progress guarantees we need to provide. The current ioend we are
* adding blocks to is cached on the writepage context, and if the new block
* does not append to the cached ioend it will create a new ioend and cache that
* instead.
*
* If a new ioend is created and cached, the old ioend is returned and queued
* locally for submission once the entire page is processed or an error has been
* detected. While ioends are submitted immediately after they are completed,
* batching optimisations are provided by higher level block plugging.
*
* At the end of a writeback pass, there will be a cached ioend remaining on the
* writepage context that the caller will need to submit.
*/
static int
xfs_writepage_map(
struct xfs_writepage_ctx *wpc,
struct writeback_control *wbc,
struct inode *inode,
struct page *page,
uint64_t end_offset)
{
LIST_HEAD(submit_list);
struct iomap_page *iop = to_iomap_page(page);
unsigned len = i_blocksize(inode);
struct xfs_ioend *ioend, *next;
uint64_t file_offset; /* file offset of page */
int error = 0, count = 0, i;
ASSERT(iop || i_blocksize(inode) == PAGE_SIZE);
ASSERT(!iop || atomic_read(&iop->write_count) == 0);
/*
* Walk through the page to find areas to write back. If we run off the
* end of the current map or find the current map invalid, grab a new
* one.
*/
for (i = 0, file_offset = page_offset(page);
i < (PAGE_SIZE >> inode->i_blkbits) && file_offset < end_offset;
i++, file_offset += len) {
if (iop && !test_bit(i, iop->uptodate))
continue;
error = xfs_map_blocks(wpc, inode, file_offset);
if (error)
break;
if (wpc->io_type == XFS_IO_HOLE)
continue;
xfs_add_to_ioend(inode, file_offset, page, iop, wpc, wbc,
&submit_list);
count++;
}
ASSERT(wpc->ioend || list_empty(&submit_list));
ASSERT(PageLocked(page));
ASSERT(!PageWriteback(page));
/*
* On error, we have to fail the ioend here because we may have set
* pages under writeback, we have to make sure we run IO completion to
* mark the error state of the IO appropriately, so we can't cancel the
* ioend directly here. That means we have to mark this page as under
* writeback if we included any blocks from it in the ioend chain so
* that completion treats it correctly.
*
* If we didn't include the page in the ioend, the on error we can
* simply discard and unlock it as there are no other users of the page
* now. The caller will still need to trigger submission of outstanding
* ioends on the writepage context so they are treated correctly on
* error.
*/
if (unlikely(error)) {
if (!count) {
xfs_aops_discard_page(page);
ClearPageUptodate(page);
unlock_page(page);
goto done;
}
/*
* If the page was not fully cleaned, we need to ensure that the
* higher layers come back to it correctly. That means we need
* to keep the page dirty, and for WB_SYNC_ALL writeback we need
* to ensure the PAGECACHE_TAG_TOWRITE index mark is not removed
* so another attempt to write this page in this writeback sweep
* will be made.
*/
set_page_writeback_keepwrite(page);
} else {
clear_page_dirty_for_io(page);
set_page_writeback(page);
}
unlock_page(page);
/*
* Preserve the original error if there was one, otherwise catch
* submission errors here and propagate into subsequent ioend
* submissions.
*/
list_for_each_entry_safe(ioend, next, &submit_list, io_list) {
int error2;
list_del_init(&ioend->io_list);
error2 = xfs_submit_ioend(wbc, ioend, error);
if (error2 && !error)
error = error2;
}
/*
* We can end up here with no error and nothing to write only if we race
* with a partial page truncate on a sub-page block sized filesystem.
*/
if (!count)
end_page_writeback(page);
done:
mapping_set_error(page->mapping, error);
return error;
}
/*
* Write out a dirty page.
*
* For delalloc space on the page we need to allocate space and flush it.
* For unwritten space on the page we need to start the conversion to
* regular allocated space.
*/
STATIC int
xfs_do_writepage(
struct page *page,
struct writeback_control *wbc,
void *data)
{
struct xfs_writepage_ctx *wpc = data;
struct inode *inode = page->mapping->host;
loff_t offset;
uint64_t end_offset;
pgoff_t end_index;
trace_xfs_writepage(inode, page, 0, 0);
/*
* Refuse to write the page out if we are called from reclaim context.
*
* This avoids stack overflows when called from deeply used stacks in
* random callers for direct reclaim or memcg reclaim. We explicitly
* allow reclaim from kswapd as the stack usage there is relatively low.
*
* This should never happen except in the case of a VM regression so
* warn about it.
*/
if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
PF_MEMALLOC))
goto redirty;
/*
* Given that we do not allow direct reclaim to call us, we should
* never be called while in a filesystem transaction.
*/
if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS))
goto redirty;
/*
* Is this page beyond the end of the file?
*
* The page index is less than the end_index, adjust the end_offset
* to the highest offset that this page should represent.
* -----------------------------------------------------
* | file mapping | <EOF> |
* -----------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | |
* ^--------------------------------^----------|--------
* | desired writeback range | see else |
* ---------------------------------^------------------|
*/
offset = i_size_read(inode);
end_index = offset >> PAGE_SHIFT;
if (page->index < end_index)
end_offset = (xfs_off_t)(page->index + 1) << PAGE_SHIFT;
else {
/*
* Check whether the page to write out is beyond or straddles
* i_size or not.
* -------------------------------------------------------
* | file mapping | <EOF> |
* -------------------------------------------------------
* | Page ... | Page N-2 | Page N-1 | Page N | Beyond |
* ^--------------------------------^-----------|---------
* | | Straddles |
* ---------------------------------^-----------|--------|
*/
unsigned offset_into_page = offset & (PAGE_SIZE - 1);
/*
* Skip the page if it is fully outside i_size, e.g. due to a
* truncate operation that is in progress. We must redirty the
* page so that reclaim stops reclaiming it. Otherwise
* xfs_vm_releasepage() is called on it and gets confused.
*
* Note that the end_index is unsigned long, it would overflow
* if the given offset is greater than 16TB on 32-bit system
* and if we do check the page is fully outside i_size or not
* via "if (page->index >= end_index + 1)" as "end_index + 1"
* will be evaluated to 0. Hence this page will be redirtied
* and be written out repeatedly which would result in an
* infinite loop, the user program that perform this operation
* will hang. Instead, we can verify this situation by checking
* if the page to write is totally beyond the i_size or if it's
* offset is just equal to the EOF.
*/
if (page->index > end_index ||
(page->index == end_index && offset_into_page == 0))
goto redirty;
/*
* The page straddles i_size. It must be zeroed out on each
* and every writepage invocation because it may be mmapped.
* "A file is mapped in multiples of the page size. For a file
* that is not a multiple of the page size, the remaining
* memory is zeroed when mapped, and writes to that region are
* not written out to the file."
*/
zero_user_segment(page, offset_into_page, PAGE_SIZE);
/* Adjust the end_offset to the end of file */
end_offset = offset;
}
return xfs_writepage_map(wpc, wbc, inode, page, end_offset);
redirty:
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
}
STATIC int
xfs_vm_writepage(
struct page *page,
struct writeback_control *wbc)
{
struct xfs_writepage_ctx wpc = {
.io_type = XFS_IO_HOLE,
};
int ret;
ret = xfs_do_writepage(page, wbc, &wpc);
if (wpc.ioend)
ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
return ret;
}
STATIC int
xfs_vm_writepages(
struct address_space *mapping,
struct writeback_control *wbc)
{
struct xfs_writepage_ctx wpc = {
.io_type = XFS_IO_HOLE,
};
int ret;
xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
ret = write_cache_pages(mapping, wbc, xfs_do_writepage, &wpc);
if (wpc.ioend)
ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
return ret;
}
STATIC int
xfs_dax_writepages(
struct address_space *mapping,
struct writeback_control *wbc)
{
xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
return dax_writeback_mapping_range(mapping,
xfs_find_bdev_for_inode(mapping->host), wbc);
}
STATIC int
xfs_vm_releasepage(
struct page *page,
gfp_t gfp_mask)
{
trace_xfs_releasepage(page->mapping->host, page, 0, 0);
return iomap_releasepage(page, gfp_mask);
}
STATIC sector_t
xfs_vm_bmap(
struct address_space *mapping,
sector_t block)
{
struct xfs_inode *ip = XFS_I(mapping->host);
trace_xfs_vm_bmap(ip);
/*
* The swap code (ab-)uses ->bmap to get a block mapping and then
* bypasses the file system for actual I/O. We really can't allow
* that on reflinks inodes, so we have to skip out here. And yes,
* 0 is the magic code for a bmap error.
*
* Since we don't pass back blockdev info, we can't return bmap
* information for rt files either.
*/
if (xfs_is_reflink_inode(ip) || XFS_IS_REALTIME_INODE(ip))
return 0;
return iomap_bmap(mapping, block, &xfs_iomap_ops);
}
STATIC int
xfs_vm_readpage(
struct file *unused,
struct page *page)
{
trace_xfs_vm_readpage(page->mapping->host, 1);
return iomap_readpage(page, &xfs_iomap_ops);
}
STATIC int
xfs_vm_readpages(
struct file *unused,
struct address_space *mapping,
struct list_head *pages,
unsigned nr_pages)
{
trace_xfs_vm_readpages(mapping->host, nr_pages);
return iomap_readpages(mapping, pages, nr_pages, &xfs_iomap_ops);
}
static int
xfs_iomap_swapfile_activate(
struct swap_info_struct *sis,
struct file *swap_file,
sector_t *span)
{
sis->bdev = xfs_find_bdev_for_inode(file_inode(swap_file));
return iomap_swapfile_activate(sis, swap_file, span, &xfs_iomap_ops);
}
const struct address_space_operations xfs_address_space_operations = {
.readpage = xfs_vm_readpage,
.readpages = xfs_vm_readpages,
.writepage = xfs_vm_writepage,
.writepages = xfs_vm_writepages,
.set_page_dirty = iomap_set_page_dirty,
.releasepage = xfs_vm_releasepage,
.invalidatepage = xfs_vm_invalidatepage,
.bmap = xfs_vm_bmap,
.direct_IO = noop_direct_IO,
.migratepage = iomap_migrate_page,
.is_partially_uptodate = iomap_is_partially_uptodate,
.error_remove_page = generic_error_remove_page,
.swap_activate = xfs_iomap_swapfile_activate,
};
const struct address_space_operations xfs_dax_aops = {
.writepages = xfs_dax_writepages,
.direct_IO = noop_direct_IO,
.set_page_dirty = noop_set_page_dirty,
.invalidatepage = noop_invalidatepage,
.swap_activate = xfs_iomap_swapfile_activate,
};