linux/fs/xfs/xfs_log.h

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/*
* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __XFS_LOG_H__
#define __XFS_LOG_H__
struct xfs_log_vec {
struct xfs_log_vec *lv_next; /* next lv in build list */
int lv_niovecs; /* number of iovecs in lv */
struct xfs_log_iovec *lv_iovecp; /* iovec array */
struct xfs_log_item *lv_item; /* owner */
char *lv_buf; /* formatted buffer */
xfs: log vector rounding leaks log space The addition of direct formatting of log items into the CIL linear buffer added alignment restrictions that the start of each vector needed to be 64 bit aligned. Hence padding was added in xlog_finish_iovec() to round up the vector length to ensure the next vector started with the correct alignment. This adds a small number of bytes to the size of the linear buffer that is otherwise unused. The issue is that we then use the linear buffer size to determine the log space used by the log item, and this includes the unused space. Hence when we account for space used by the log item, it's more than is actually written into the iclogs, and hence we slowly leak this space. This results on log hangs when reserving space, with threads getting stuck with these stack traces: Call Trace: [<ffffffff81d15989>] schedule+0x29/0x70 [<ffffffff8150d3a2>] xlog_grant_head_wait+0xa2/0x1a0 [<ffffffff8150d55d>] xlog_grant_head_check+0xbd/0x140 [<ffffffff8150ee33>] xfs_log_reserve+0x103/0x220 [<ffffffff814b7f05>] xfs_trans_reserve+0x2f5/0x310 ..... The 4 bytes is significant. Brain Foster did all the hard work in tracking down a reproducable leak to inode chunk allocation (it went away with the ikeep mount option). His rough numbers were that creating 50,000 inodes leaked 11 log blocks. This turns out to be roughly 800 inode chunks or 1600 inode cluster buffers. That works out at roughly 4 bytes per cluster buffer logged, and at that I started looking for a 4 byte leak in the buffer logging code. What I found was that a struct xfs_buf_log_format structure for an inode cluster buffer is 28 bytes in length. This gets rounded up to 32 bytes, but the vector length remains 28 bytes. Hence the CIL ticket reservation is decremented by 32 bytes (via lv->lv_buf_len) for that vector rather than 28 bytes which are written into the log. The fix for this problem is to separately track the bytes used by the log vectors in the item and use that instead of the buffer length when accounting for the log space that will be used by the formatted log item. Again, thanks to Brian Foster for doing all the hard work and long hours to isolate this leak and make finding the bug relatively simple. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2014-05-19 22:18:09 +00:00
int lv_bytes; /* accounted space in buffer */
int lv_buf_len; /* aligned size of buffer */
int lv_size; /* size of allocated lv */
};
#define XFS_LOG_VEC_ORDERED (-1)
static inline void *
xlog_prepare_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec **vecp,
uint type)
{
struct xfs_log_iovec *vec = *vecp;
if (vec) {
ASSERT(vec - lv->lv_iovecp < lv->lv_niovecs);
vec++;
} else {
vec = &lv->lv_iovecp[0];
}
vec->i_type = type;
vec->i_addr = lv->lv_buf + lv->lv_buf_len;
ASSERT(IS_ALIGNED((unsigned long)vec->i_addr, sizeof(uint64_t)));
*vecp = vec;
return vec->i_addr;
}
xfs: log vector rounding leaks log space The addition of direct formatting of log items into the CIL linear buffer added alignment restrictions that the start of each vector needed to be 64 bit aligned. Hence padding was added in xlog_finish_iovec() to round up the vector length to ensure the next vector started with the correct alignment. This adds a small number of bytes to the size of the linear buffer that is otherwise unused. The issue is that we then use the linear buffer size to determine the log space used by the log item, and this includes the unused space. Hence when we account for space used by the log item, it's more than is actually written into the iclogs, and hence we slowly leak this space. This results on log hangs when reserving space, with threads getting stuck with these stack traces: Call Trace: [<ffffffff81d15989>] schedule+0x29/0x70 [<ffffffff8150d3a2>] xlog_grant_head_wait+0xa2/0x1a0 [<ffffffff8150d55d>] xlog_grant_head_check+0xbd/0x140 [<ffffffff8150ee33>] xfs_log_reserve+0x103/0x220 [<ffffffff814b7f05>] xfs_trans_reserve+0x2f5/0x310 ..... The 4 bytes is significant. Brain Foster did all the hard work in tracking down a reproducable leak to inode chunk allocation (it went away with the ikeep mount option). His rough numbers were that creating 50,000 inodes leaked 11 log blocks. This turns out to be roughly 800 inode chunks or 1600 inode cluster buffers. That works out at roughly 4 bytes per cluster buffer logged, and at that I started looking for a 4 byte leak in the buffer logging code. What I found was that a struct xfs_buf_log_format structure for an inode cluster buffer is 28 bytes in length. This gets rounded up to 32 bytes, but the vector length remains 28 bytes. Hence the CIL ticket reservation is decremented by 32 bytes (via lv->lv_buf_len) for that vector rather than 28 bytes which are written into the log. The fix for this problem is to separately track the bytes used by the log vectors in the item and use that instead of the buffer length when accounting for the log space that will be used by the formatted log item. Again, thanks to Brian Foster for doing all the hard work and long hours to isolate this leak and make finding the bug relatively simple. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2014-05-19 22:18:09 +00:00
/*
* We need to make sure the next buffer is naturally aligned for the biggest
* basic data type we put into it. We already accounted for this padding when
* sizing the buffer.
*
* However, this padding does not get written into the log, and hence we have to
* track the space used by the log vectors separately to prevent log space hangs
* due to inaccurate accounting (i.e. a leak) of the used log space through the
* CIL context ticket.
*/
static inline void
xlog_finish_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec *vec, int len)
{
lv->lv_buf_len += round_up(len, sizeof(uint64_t));
xfs: log vector rounding leaks log space The addition of direct formatting of log items into the CIL linear buffer added alignment restrictions that the start of each vector needed to be 64 bit aligned. Hence padding was added in xlog_finish_iovec() to round up the vector length to ensure the next vector started with the correct alignment. This adds a small number of bytes to the size of the linear buffer that is otherwise unused. The issue is that we then use the linear buffer size to determine the log space used by the log item, and this includes the unused space. Hence when we account for space used by the log item, it's more than is actually written into the iclogs, and hence we slowly leak this space. This results on log hangs when reserving space, with threads getting stuck with these stack traces: Call Trace: [<ffffffff81d15989>] schedule+0x29/0x70 [<ffffffff8150d3a2>] xlog_grant_head_wait+0xa2/0x1a0 [<ffffffff8150d55d>] xlog_grant_head_check+0xbd/0x140 [<ffffffff8150ee33>] xfs_log_reserve+0x103/0x220 [<ffffffff814b7f05>] xfs_trans_reserve+0x2f5/0x310 ..... The 4 bytes is significant. Brain Foster did all the hard work in tracking down a reproducable leak to inode chunk allocation (it went away with the ikeep mount option). His rough numbers were that creating 50,000 inodes leaked 11 log blocks. This turns out to be roughly 800 inode chunks or 1600 inode cluster buffers. That works out at roughly 4 bytes per cluster buffer logged, and at that I started looking for a 4 byte leak in the buffer logging code. What I found was that a struct xfs_buf_log_format structure for an inode cluster buffer is 28 bytes in length. This gets rounded up to 32 bytes, but the vector length remains 28 bytes. Hence the CIL ticket reservation is decremented by 32 bytes (via lv->lv_buf_len) for that vector rather than 28 bytes which are written into the log. The fix for this problem is to separately track the bytes used by the log vectors in the item and use that instead of the buffer length when accounting for the log space that will be used by the formatted log item. Again, thanks to Brian Foster for doing all the hard work and long hours to isolate this leak and make finding the bug relatively simple. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2014-05-19 22:18:09 +00:00
lv->lv_bytes += len;
vec->i_len = len;
}
static inline void *
xlog_copy_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec **vecp,
uint type, void *data, int len)
{
void *buf;
buf = xlog_prepare_iovec(lv, vecp, type);
memcpy(buf, data, len);
xlog_finish_iovec(lv, *vecp, len);
return buf;
}
/*
* Structure used to pass callback function and the function's argument
* to the log manager.
*/
typedef struct xfs_log_callback {
struct xfs_log_callback *cb_next;
void (*cb_func)(void *, int);
void *cb_arg;
} xfs_log_callback_t;
/*
* By comparing each component, we don't have to worry about extra
* endian issues in treating two 32 bit numbers as one 64 bit number
*/
static inline xfs_lsn_t _lsn_cmp(xfs_lsn_t lsn1, xfs_lsn_t lsn2)
{
if (CYCLE_LSN(lsn1) != CYCLE_LSN(lsn2))
return (CYCLE_LSN(lsn1)<CYCLE_LSN(lsn2))? -999 : 999;
if (BLOCK_LSN(lsn1) != BLOCK_LSN(lsn2))
return (BLOCK_LSN(lsn1)<BLOCK_LSN(lsn2))? -999 : 999;
return 0;
}
#define XFS_LSN_CMP(x,y) _lsn_cmp(x,y)
/*
* Flags to xfs_log_force()
*
* XFS_LOG_SYNC: Synchronous force in-core log to disk
*/
#define XFS_LOG_SYNC 0x1
/* Log manager interfaces */
struct xfs_mount;
struct xlog_in_core;
struct xlog_ticket;
struct xfs_log_item;
struct xfs_item_ops;
struct xfs_trans;
xfs_lsn_t xfs_log_done(struct xfs_mount *mp,
struct xlog_ticket *ticket,
struct xlog_in_core **iclog,
bool regrant);
int _xfs_log_force(struct xfs_mount *mp,
uint flags,
int *log_forced);
void xfs_log_force(struct xfs_mount *mp,
uint flags);
int _xfs_log_force_lsn(struct xfs_mount *mp,
xfs_lsn_t lsn,
uint flags,
int *log_forced);
void xfs_log_force_lsn(struct xfs_mount *mp,
xfs_lsn_t lsn,
uint flags);
int xfs_log_mount(struct xfs_mount *mp,
struct xfs_buftarg *log_target,
xfs_daddr_t start_block,
int num_bblocks);
int xfs_log_mount_finish(struct xfs_mount *mp);
int xfs_log_mount_cancel(struct xfs_mount *);
xfs_lsn_t xlog_assign_tail_lsn(struct xfs_mount *mp);
xfs_lsn_t xlog_assign_tail_lsn_locked(struct xfs_mount *mp);
void xfs_log_space_wake(struct xfs_mount *mp);
int xfs_log_notify(struct xfs_mount *mp,
struct xlog_in_core *iclog,
struct xfs_log_callback *callback_entry);
int xfs_log_release_iclog(struct xfs_mount *mp,
struct xlog_in_core *iclog);
int xfs_log_reserve(struct xfs_mount *mp,
int length,
int count,
struct xlog_ticket **ticket,
uint8_t clientid,
bool permanent);
int xfs_log_regrant(struct xfs_mount *mp, struct xlog_ticket *tic);
void xfs_log_unmount(struct xfs_mount *mp);
int xfs_log_force_umount(struct xfs_mount *mp, int logerror);
xfs: Introduce delayed logging core code The delayed logging code only changes in-memory structures and as such can be enabled and disabled with a mount option. Add the mount option and emit a warning that this is an experimental feature that should not be used in production yet. We also need infrastructure to track committed items that have not yet been written to the log. This is what the Committed Item List (CIL) is for. The log item also needs to be extended to track the current log vector, the associated memory buffer and it's location in the Commit Item List. Extend the log item and log vector structures to enable this tracking. To maintain the current log format for transactions with delayed logging, we need to introduce a checkpoint transaction and a context for tracking each checkpoint from initiation to transaction completion. This includes adding a log ticket for tracking space log required/used by the context checkpoint. To track all the changes we need an io vector array per log item, rather than a single array for the entire transaction. Using the new log vector structure for this requires two passes - the first to allocate the log vector structures and chain them together, and the second to fill them out. This log vector chain can then be passed to the CIL for formatting, pinning and insertion into the CIL. Formatting of the log vector chain is relatively simple - it's just a loop over the iovecs on each log vector, but it is made slightly more complex because we re-write the iovec after the copy to point back at the memory buffer we just copied into. This code also needs to pin log items. If the log item is not already tracked in this checkpoint context, then it needs to be pinned. Otherwise it is already pinned and we don't need to pin it again. The only other complexity is calculating the amount of new log space the formatting has consumed. This needs to be accounted to the transaction in progress, and the accounting is made more complex becase we need also to steal space from it for log metadata in the checkpoint transaction. Calculate all this at insert time and update all the tickets, counters, etc correctly. Once we've formatted all the log items in the transaction, attach the busy extents to the checkpoint context so the busy extents live until checkpoint completion and can be processed at that point in time. Transactions can then be freed at this point in time. Now we need to issue checkpoints - we are tracking the amount of log space used by the items in the CIL, so we can trigger background checkpoints when the space usage gets to a certain threshold. Otherwise, checkpoints need ot be triggered when a log synchronisation point is reached - a log force event. Because the log write code already handles chained log vectors, writing the transaction is trivial, too. Construct a transaction header, add it to the head of the chain and write it into the log, then issue a commit record write. Then we can release the checkpoint log ticket and attach the context to the log buffer so it can be called during Io completion to complete the checkpoint. We also need to allow for synchronising multiple in-flight checkpoints. This is needed for two things - the first is to ensure that checkpoint commit records appear in the log in the correct sequence order (so they are replayed in the correct order). The second is so that xfs_log_force_lsn() operates correctly and only flushes and/or waits for the specific sequence it was provided with. To do this we need a wait variable and a list tracking the checkpoint commits in progress. We can walk this list and wait for the checkpoints to change state or complete easily, an this provides the necessary synchronisation for correct operation in both cases. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
2010-05-21 04:37:18 +00:00
struct xlog_ticket *xfs_log_ticket_get(struct xlog_ticket *ticket);
void xfs_log_ticket_put(struct xlog_ticket *ticket);
void xfs_log_commit_cil(struct xfs_mount *mp, struct xfs_trans *tp,
xfs_lsn_t *commit_lsn, bool regrant);
xfs: Ensure inode allocation buffers are fully replayed With delayed logging, we can get inode allocation buffers in the same transaction inode unlink buffers. We don't currently mark inode allocation buffers in the log, so inode unlink buffers take precedence over allocation buffers. The result is that when they are combined into the same checkpoint, only the unlinked inode chain fields are replayed, resulting in uninitialised inode buffers being detected when the next inode modification is replayed. To fix this, we need to ensure that we do not set the inode buffer flag in the buffer log item format flags if the inode allocation has not already hit the log. To avoid requiring a change to log recovery, we really need to make this a modification that relies only on in-memory sate. We can do this by checking during buffer log formatting (while the CIL cannot be flushed) if we are still in the same sequence when we commit the unlink transaction as the inode allocation transaction. If we are, then we do not add the inode buffer flag to the buffer log format item flags. This means the entire buffer will be replayed, not just the unlinked fields. We do this while CIL flusheѕ are locked out to ensure that we don't race with the sequence numbers changing and hence fail to put the inode buffer flag in the buffer format flags when we really need to. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
2010-05-20 13:19:42 +00:00
bool xfs_log_item_in_current_chkpt(struct xfs_log_item *lip);
xfs: Introduce delayed logging core code The delayed logging code only changes in-memory structures and as such can be enabled and disabled with a mount option. Add the mount option and emit a warning that this is an experimental feature that should not be used in production yet. We also need infrastructure to track committed items that have not yet been written to the log. This is what the Committed Item List (CIL) is for. The log item also needs to be extended to track the current log vector, the associated memory buffer and it's location in the Commit Item List. Extend the log item and log vector structures to enable this tracking. To maintain the current log format for transactions with delayed logging, we need to introduce a checkpoint transaction and a context for tracking each checkpoint from initiation to transaction completion. This includes adding a log ticket for tracking space log required/used by the context checkpoint. To track all the changes we need an io vector array per log item, rather than a single array for the entire transaction. Using the new log vector structure for this requires two passes - the first to allocate the log vector structures and chain them together, and the second to fill them out. This log vector chain can then be passed to the CIL for formatting, pinning and insertion into the CIL. Formatting of the log vector chain is relatively simple - it's just a loop over the iovecs on each log vector, but it is made slightly more complex because we re-write the iovec after the copy to point back at the memory buffer we just copied into. This code also needs to pin log items. If the log item is not already tracked in this checkpoint context, then it needs to be pinned. Otherwise it is already pinned and we don't need to pin it again. The only other complexity is calculating the amount of new log space the formatting has consumed. This needs to be accounted to the transaction in progress, and the accounting is made more complex becase we need also to steal space from it for log metadata in the checkpoint transaction. Calculate all this at insert time and update all the tickets, counters, etc correctly. Once we've formatted all the log items in the transaction, attach the busy extents to the checkpoint context so the busy extents live until checkpoint completion and can be processed at that point in time. Transactions can then be freed at this point in time. Now we need to issue checkpoints - we are tracking the amount of log space used by the items in the CIL, so we can trigger background checkpoints when the space usage gets to a certain threshold. Otherwise, checkpoints need ot be triggered when a log synchronisation point is reached - a log force event. Because the log write code already handles chained log vectors, writing the transaction is trivial, too. Construct a transaction header, add it to the head of the chain and write it into the log, then issue a commit record write. Then we can release the checkpoint log ticket and attach the context to the log buffer so it can be called during Io completion to complete the checkpoint. We also need to allow for synchronising multiple in-flight checkpoints. This is needed for two things - the first is to ensure that checkpoint commit records appear in the log in the correct sequence order (so they are replayed in the correct order). The second is so that xfs_log_force_lsn() operates correctly and only flushes and/or waits for the specific sequence it was provided with. To do this we need a wait variable and a list tracking the checkpoint commits in progress. We can walk this list and wait for the checkpoints to change state or complete easily, an this provides the necessary synchronisation for correct operation in both cases. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
2010-05-21 04:37:18 +00:00
void xfs_log_work_queue(struct xfs_mount *mp);
void xfs_log_quiesce(struct xfs_mount *mp);
xfs: validate metadata LSNs against log on v5 superblocks Since the onset of v5 superblocks, the LSN of the last modification has been included in a variety of on-disk data structures. This LSN is used to provide log recovery ordering guarantees (e.g., to ensure an older log recovery item is not replayed over a newer target data structure). While this works correctly from the point a filesystem is formatted and mounted, userspace tools have some problematic behaviors that defeat this mechanism. For example, xfs_repair historically zeroes out the log unconditionally (regardless of whether corruption is detected). If this occurs, the LSN of the filesystem is reset and the log is now in a problematic state with respect to on-disk metadata structures that might have a larger LSN. Until either the log catches up to the highest previously used metadata LSN or each affected data structure is modified and written out without incident (which resets the metadata LSN), log recovery is susceptible to filesystem corruption. This problem is ultimately addressed and repaired in the associated userspace tools. The kernel is still responsible to detect the problem and notify the user that something is wrong. Check the superblock LSN at mount time and fail the mount if it is invalid. From that point on, trigger verifier failure on any metadata I/O where an invalid LSN is detected. This results in a filesystem shutdown and guarantees that we do not log metadata changes with invalid LSNs on disk. Since this is a known issue with a known recovery path, present a warning to instruct the user how to recover. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
2015-10-12 04:59:25 +00:00
bool xfs_log_check_lsn(struct xfs_mount *, xfs_lsn_t);
#endif /* __XFS_LOG_H__ */