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d552a2b9b3
Implement truncate/delete as a non-recursive algorithm. The older algorithm was implemented with recursion to strip off each layer at a time (going by height, starting with the maximum height. This version tries to do the same thing but without recursion, and without needing to allocate new structures or lists in memory. For example, say you want to truncate a very large file to 1 byte, and its end-of-file metapath is: 0.505.463.428. The starting metapath would be 0.0.0.0. Since it's a truncate to non-zero, it needs to preserve that byte, and all metadata pointing to it. So it would start at 0.0.0.0, look up all its metadata buffers, then free all data blocks pointed to at the highest level. After that buffer is "swept", it moves on to 0.0.0.1, then 0.0.0.2, etc., reading in buffers and sweeping them clean. When it gets to the end of the 0.0.0 metadata buffer (for 4K blocks the last valid one is 0.0.0.508), it backs up to the previous height and starts working on 0.0.1.0, then 0.0.1.1, and so forth. After it reaches the end and sweeps 0.0.1.508, it continues with 0.0.2.0, and so on. When that height is exhausted, and it reaches 0.0.508.508 it backs up another level, to 0.1.0.0, then 0.1.0.1, through 0.1.0.508. So it has to keep marching backwards and forwards through the metadata until it's all swept clean. Once it has all the data blocks freed, it lowers the strip height, and begins the process all over again, but with one less height. This time it sweeps 0.0.0 through 0.505.463. When that's clean, it lowers the strip height again and works to free 0.505. Eventually it strips the lowest height, 0. For a delete or truncate to 0, all metadata for all heights of 0.0.0.0 would be freed. For a truncate to 1 byte, 0.0.0.0 would be preserved. This isn't much different from normal integer incrementing, where an integer gets incremented from 0000 (0.0.0.0) to 3021 (3.0.2.1). So 0000 gets increments to 0001, 0002, up to 0009, then on to 0010, 0011 up to 0099, then 0100 and so forth. It's just that each "digit" goes from 0 to 508 (for a total of 509 pointers) rather than from 0 to 9. Note that the dinode will only have 483 pointers due to the dinode structure itself. Also note: this is just an example. These numbers (509 and 483) are based on a standard 4K block size. Smaller block sizes will yield smaller numbers of indirect pointers accordingly. The truncation process is accomplished with the help of two major functions and a few helper functions. Functions do_strip and recursive_scan are obsolete, so removed. New function sweep_bh_for_rgrps cleans a buffer_head pointed to by the given metapath and height. By cleaning, I mean it frees all blocks starting at the offset passed in metapath. It starts at the first block in the buffer pointed to by the metapath and identifies its resource group (rgrp). From there it frees all subsequent block pointers that lie within that rgrp. If it's already inside a transaction, it stays within it as long as it can. In other words, it doesn't close a transaction until it knows it's freed what it can from the resource group. In this way, multiple buffers may be cleaned in a single transaction, as long as those blocks in the buffer all lie within the same rgrp. If it's not in a transaction, it starts one. If the buffer_head has references to blocks within multiple rgrps, it frees all the blocks inside the first rgrp it finds, then closes the transaction. Then it repeats the cycle: identifies the next unfreed block, uses it to find its rgrp, then starts a new transaction for that set. It repeats this process repeatedly until the buffer_head contains no more references to any blocks past the given metapath. Function trunc_dealloc has been reworked into a finite state automaton. It has basically 3 active states: DEALLOC_MP_FULL, DEALLOC_MP_LOWER, and DEALLOC_FILL_MP: The DEALLOC_MP_FULL state implies the metapath has a full set of buffers out to the "shrink height", and therefore, it can call function sweep_bh_for_rgrps to free the blocks within the highest height of the metapath. If it's just swept the lowest level (or an error has occurred) the state machine is ended. Otherwise it proceeds to the DEALLOC_MP_LOWER state. The DEALLOC_MP_LOWER state implies we are finished with a given buffer_head, which may now be released, and therefore we are then missing some buffer information from the metapath. So we need to find more buffers to read in. In most cases, this is just a matter of releasing the buffer_head and moving to the next pointer from the previous height, so it may be read in and swept as well. If it can't find another non-null pointer to process, it checks whether it's reached the end of a height and needs to lower the strip height, or whether it still needs move forward through the previous height's metadata. In this state, all zero-pointers are skipped. From this state, it can only loop around (once more backing up another height) or, once a valid metapath is found (one that has non-zero pointers), proceed to state DEALLOC_FILL_MP. The DEALLOC_FILL_MP state implies that we have a metapath but not all its buffers are read in. So we must proceed to read in buffer_heads until the metapath has a valid buffer for every height. If the previous state backed us up 3 heights, we may need to read in a buffer, increment the height, then repeat the process until buffers have been read in for all required heights. If it's successful reading a buffer, and it's at the highest height we need, it proceeds back to the DEALLOC_MP_FULL state. If it's unable to fill in a buffer, (encounters a hole, etc.) it tries to find another non-zero block pointer. If they're all zero, it lowers the height and returns to the DEALLOC_MP_LOWER state. If it finds a good non-null pointer, it loops around and reads it in, while keeping the metapath in lock-step with the pointers it examines. The state machine runs until the truncation request is satisfied. Then any transactions are ended, the quota and statfs data are updated, and the function is complete. Helper function metaptr1 was introduced to be an easy way to determine the start of a buffer_head's indirect pointers. Helper function lookup_mp_height was introduced to find a metapath index and read in the buffer that corresponds to it. In this way, function lookup_metapath becomes a simple loop to call it for every height. Helper function fillup_metapath is similar to lookup_metapath except it can do partial lookups. If the state machine backed up multiple levels (like 2999 wrapping to 3000) it needs to find out the next starting point and start issuing metadata reads at that point. Helper function hptrs is a shortcut to determine how many pointers should be expected in a buffer. Height 0 is the dinode which has fewer pointers than the others. Signed-off-by: Bob Peterson <rpeterso@redhat.com>
94 lines
3.5 KiB
C
94 lines
3.5 KiB
C
/*
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* Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
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* Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU General Public License version 2.
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*/
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#ifndef __RGRP_DOT_H__
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#define __RGRP_DOT_H__
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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/* Since each block in the file system is represented by two bits in the
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* bitmap, one 64-bit word in the bitmap will represent 32 blocks.
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* By reserving 32 blocks at a time, we can optimize / shortcut how we search
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* through the bitmaps by looking a word at a time.
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*/
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#define RGRP_RSRV_MINBYTES 8
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#define RGRP_RSRV_MINBLKS ((u32)(RGRP_RSRV_MINBYTES * GFS2_NBBY))
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#define RGRP_RSRV_ADDBLKS 64
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struct gfs2_rgrpd;
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struct gfs2_sbd;
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struct gfs2_holder;
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extern void gfs2_rgrp_verify(struct gfs2_rgrpd *rgd);
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extern struct gfs2_rgrpd *gfs2_blk2rgrpd(struct gfs2_sbd *sdp, u64 blk, bool exact);
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extern struct gfs2_rgrpd *gfs2_rgrpd_get_first(struct gfs2_sbd *sdp);
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extern struct gfs2_rgrpd *gfs2_rgrpd_get_next(struct gfs2_rgrpd *rgd);
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extern void gfs2_clear_rgrpd(struct gfs2_sbd *sdp);
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extern int gfs2_rindex_update(struct gfs2_sbd *sdp);
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extern void gfs2_free_clones(struct gfs2_rgrpd *rgd);
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extern int gfs2_rgrp_go_lock(struct gfs2_holder *gh);
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extern void gfs2_rgrp_brelse(struct gfs2_rgrpd *rgd);
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extern void gfs2_rgrp_go_unlock(struct gfs2_holder *gh);
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extern struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip);
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#define GFS2_AF_ORLOV 1
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extern int gfs2_inplace_reserve(struct gfs2_inode *ip,
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struct gfs2_alloc_parms *ap);
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extern void gfs2_inplace_release(struct gfs2_inode *ip);
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extern int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *n,
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bool dinode, u64 *generation);
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extern int gfs2_rsqa_alloc(struct gfs2_inode *ip);
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extern void gfs2_rs_deltree(struct gfs2_blkreserv *rs);
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extern void gfs2_rsqa_delete(struct gfs2_inode *ip, atomic_t *wcount);
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extern void __gfs2_free_blocks(struct gfs2_inode *ip, u64 bstart, u32 blen, int meta);
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extern void gfs2_free_meta(struct gfs2_inode *ip, u64 bstart, u32 blen);
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extern void gfs2_free_di(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip);
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extern void gfs2_unlink_di(struct inode *inode);
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extern int gfs2_check_blk_type(struct gfs2_sbd *sdp, u64 no_addr,
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unsigned int type);
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struct gfs2_rgrp_list {
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unsigned int rl_rgrps;
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unsigned int rl_space;
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struct gfs2_rgrpd **rl_rgd;
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struct gfs2_holder *rl_ghs;
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};
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extern void gfs2_rlist_add(struct gfs2_inode *ip, struct gfs2_rgrp_list *rlist,
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u64 block);
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extern void gfs2_rlist_alloc(struct gfs2_rgrp_list *rlist, unsigned int state);
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extern void gfs2_rlist_free(struct gfs2_rgrp_list *rlist);
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extern u64 gfs2_ri_total(struct gfs2_sbd *sdp);
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extern void gfs2_rgrp_dump(struct seq_file *seq, const struct gfs2_glock *gl);
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extern int gfs2_rgrp_send_discards(struct gfs2_sbd *sdp, u64 offset,
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struct buffer_head *bh,
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const struct gfs2_bitmap *bi, unsigned minlen, u64 *ptrimmed);
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extern int gfs2_fitrim(struct file *filp, void __user *argp);
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/* This is how to tell if a reservation is in the rgrp tree: */
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static inline bool gfs2_rs_active(const struct gfs2_blkreserv *rs)
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{
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return rs && !RB_EMPTY_NODE(&rs->rs_node);
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}
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static inline int rgrp_contains_block(struct gfs2_rgrpd *rgd, u64 block)
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{
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u64 first = rgd->rd_data0;
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u64 last = first + rgd->rd_data;
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return first <= block && block < last;
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}
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extern void check_and_update_goal(struct gfs2_inode *ip);
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#endif /* __RGRP_DOT_H__ */
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