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2009-12-14md: add MODULE_DESCRIPTION for all md related modules.NeilBrown
Suggested by Oren Held <orenhe@il.ibm.com> Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14raid: improve MD/raid10 handling of correctable read errors.Robert Becker
We've noticed severe lasting performance degradation of our raid arrays when we have drives that yield large amounts of media errors. The raid10 module will queue each failed read for retry, and also will attempt call fix_read_error() to perform the read recovery. Read recovery is performed while the array is frozen, so repeated recovery attempts can degrade the performance of the array for extended periods of time. With this patch I propose adding a per md device max number of corrected read attempts. Each rdev will maintain a count of read correction attempts in the rdev->read_errors field (not used currently for raid10). When we enter fix_read_error() we'll check to see when the last read error occurred, and divide the read error count by 2 for every hour since the last read error. If at that point our read error count exceeds the read error threshold, we'll fail the raid device. In addition in this patch I add sysfs nodes (get/set) for the per md max_read_errors attribute, the rdev->read_errors attribute, and added some printk's to indicate when fix_read_error fails to repair an rdev. For testing I used debugfs->fail_make_request to inject IO errors to the rdev while doing IO to the raid array. Signed-off-by: Robert Becker <Rob.Becker@riverbed.com> Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/raid10: print more useful messages on device failure.Robert Becker
When we get a read error on a device in a RAID10, and attempting to repair the error fails, print more useful messages about why it failed. Signed-off-by: Robert Becker <Rob.Becker@riverbed.com> Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/bitmap: update dirty flag when bitmap bits are explicitly set.NeilBrown
There is a sysfs file which allows bits in the write-intent bitmap to be explicit set - indicating that the block is thought to be 'dirty'. When this happens we should really set recovery_cp backwards to include the block to reflect this dirtiness. In particular, a 'resync' process will refuse to start if recovery_cp is beyond the end of the array, so this is needed to allow a resync to be triggered. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: Support write-intent bitmaps with externally managed metadata.NeilBrown
In this case, the metadata needs to not be in the same sector as the bitmap. md will not read/write any bitmap metadata. Config must be done via sysfs and when a recovery makes the array non-degraded again, writing 'true' to 'bitmap/can_clear' will allow bits in the bitmap to be cleared again. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/bitmap: move setting of daemon_lastrun out of bitmap_read_sbNeilBrown
Setting daemon_lastrun really has nothing to do with reading the bitmap superblock, it just happens to be needed at the same time. bitmap_read_sb is about to become options, so move that code out to after the call to bitmap_read_sb. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: support updating bitmap parameters via sysfs.NeilBrown
A new attribute directory 'bitmap' in 'md' is created which contains files for configuring the bitmap. 'location' identifies where the bitmap is, either 'none', or 'file' or 'sector offset from metadata'. Writing 'location' can create or remove a bitmap. Adding a 'file' bitmap this way is not yet supported. 'chunksize' and 'time_base' must be set before 'location' can be set. 'chunksize' can be set before creating a bitmap, but is currently always over-ridden by the bitmap superblock. 'time_base' and 'backlog' can be updated at any time. Signed-off-by: NeilBrown <neilb@suse.de> Reviewed-by: Andre Noll <maan@systemlinux.org>
2009-12-14md: factor out parsing of fixed-point numbersNeilBrown
safe_delay_store can parse fixed point numbers (for fractions of a second). We will want to do that for another sysfs file soon, so factor out the code. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: support bitmap offset appropriate for external-metadata arrays.NeilBrown
For md arrays were metadata is managed externally, the kernel does not know about a superblock so the superblock offset is 0. If we want to have a write-intent-bitmap near the end of the devices of such an array, we should support sector_t sized offset. We need offset be possibly negative for when the bitmap is before the metadata, so use loff_t instead. Also add sanity check that bitmap does not overlap with data. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: remove needless setting of thread->timeout in raid10_quiesceNeilBrown
As bitmap_create and bitmap_destroy already set thread->timeout as appropriate, there is no need to do it in raid10_quiesce. There is a possible need to wake the thread after the timeout has been set low, but it is better to do that where the timeout is actually set low, in bitmap_create. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: change daemon_sleep to be in 'jiffies' rather than 'seconds'.NeilBrown
This removes a lot of multiplications by HZ. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: move offset, daemon_sleep and chunksize out of bitmap structureNeilBrown
... and into bitmap_info. These are all configuration parameters that need to be set before the bitmap is created. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: collect bitmap-specific fields into one structure.NeilBrown
In preparation for making bitmap fields configurable via sysfs, start tidying up by making a single structure to contain the configuration fields. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/raid1: add takeover support for raid5->raid1NeilBrown
A 2-device raid5 array can now be converted to raid1. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: add honouring of suspend_{lo,hi} to raid1.NeilBrown
This will allow us to stop writeout to portions of the array while they are resynced by someone else - e.g. another node in a cluster. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/raid5: don't complete make_request on barrier until writes are scheduledNeilBrown
The post-barrier-flush is sent by md as soon as make_request on the barrier write completes. For raid5, the data might not be in the per-device queues yet. So for barrier requests, wait for any pre-reading to be done so that the request will be in the per-device queues. We use the 'preread_active' count to check that nothing is still in the preread phase, and delay the decrement of this count until after write requests have been submitted to the underlying devices. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: support barrier requests on all personalities.NeilBrown
Previously barriers were only supported on RAID1. This is because other levels requires synchronisation across all devices and so needed a different approach. Here is that approach. When a barrier arrives, we send a zero-length barrier to every active device. When that completes - and if the original request was not empty - we submit the barrier request itself (with the barrier flag cleared) and then submit a fresh load of zero length barriers. The barrier request itself is asynchronous, but any subsequent request will block until the barrier completes. The reason for clearing the barrier flag is that a barrier request is allowed to fail. If we pass a non-empty barrier through a striping raid level it is conceivable that part of it could succeed and part could fail. That would be way too hard to deal with. So if the first run of zero length barriers succeed, we assume all is sufficiently well that we send the request and ignore errors in the second run of barriers. RAID5 needs extra care as write requests may not have been submitted to the underlying devices yet. So we flush the stripe cache before proceeding with the barrier. Note that the second set of zero-length barriers are submitted immediately after the original request is submitted. Thus when a personality finds mddev->barrier to be set during make_request, it should not return from make_request until the corresponding per-device request(s) have been queued. That will be done in later patches. Signed-off-by: NeilBrown <neilb@suse.de> Reviewed-by: Andre Noll <maan@systemlinux.org>
2009-12-14md: don't reset curr_resync_completed after an interrupted resyncNeilBrown
If a resync/recovery/check/repair is interrupted for some reason, it can be useful to know exactly where it got up to. So in that case, do not clear curr_resync_completed. Initialise it when starting a resync/recovery/... instead. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: adjust resync_min usefully when resync aborts.NeilBrown
When a 'check' or 'repair' finished we should clear resync_min so that a future check/repair will cover the whole array (by default). However if it is interrupted, we should update resync_min to where we got up to, so that when the check/repair continues it just does the remainder of the array. Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md: remove sparse warning:symbol XXX was not declared.NeilBrown
Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/raid5: remove some sparse warnings.NeilBrown
qd_idx is previously declared and given exactly the same value! Signed-off-by: NeilBrown <neilb@suse.de>
2009-12-14md/bitmap: protect against bitmap removal while being updated.NeilBrown
A write intent bitmap can be removed from an array while the array is active. When this happens, all IO is suspended and flushed before the bitmap is removed. However it is possible that bitmap_daemon_work is still running to clear old bits from the bitmap. If it is, it can dereference the bitmap after it has been freed. So introduce a new mutex to protect bitmap_daemon_work and get it before destroying a bitmap. This is suitable for any current -stable kernel. Signed-off-by: NeilBrown <neilb@suse.de> Cc: stable@kernel.org
2009-12-09Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (42 commits) tree-wide: fix misspelling of "definition" in comments reiserfs: fix misspelling of "journaled" doc: Fix a typo in slub.txt. inotify: remove superfluous return code check hdlc: spelling fix in find_pvc() comment doc: fix regulator docs cut-and-pasteism mtd: Fix comment in Kconfig doc: Fix IRQ chip docs tree-wide: fix assorted typos all over the place drivers/ata/libata-sff.c: comment spelling fixes fix typos/grammos in Documentation/edac.txt sysctl: add missing comments fs/debugfs/inode.c: fix comment typos sgivwfb: Make use of ARRAY_SIZE. sky2: fix sky2_link_down copy/paste comment error tree-wide: fix typos "couter" -> "counter" tree-wide: fix typos "offest" -> "offset" fix kerneldoc for set_irq_msi() spidev: fix double "of of" in comment comment typo fix: sybsystem -> subsystem ...
2009-12-09Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6Linus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6: (222 commits) [SCSI] zfcp: Remove flag ZFCP_STATUS_FSFREQ_TMFUNCNOTSUPP [SCSI] zfcp: Activate fc4s attributes for zfcp in FC transport class [SCSI] zfcp: Block scsi_eh thread for rport state BLOCKED [SCSI] zfcp: Update FSF error reporting [SCSI] zfcp: Improve ELS ADISC handling [SCSI] zfcp: Simplify handling of ct and els requests [SCSI] zfcp: Remove ZFCP_DID_MASK [SCSI] zfcp: Move WKA port to zfcp FC code [SCSI] zfcp: Use common code definitions for FC CT structs [SCSI] zfcp: Use common code definitions for FC ELS structs [SCSI] zfcp: Update FCP protocol related code [SCSI] zfcp: Dont fail SCSI commands when transitioning to blocked fc_rport [SCSI] zfcp: Assign scheduled work to driver queue [SCSI] zfcp: Remove STATUS_COMMON_REMOVE flag as it is not required anymore [SCSI] zfcp: Implement module unloading [SCSI] zfcp: Merge trace code for fsf requests in one function [SCSI] zfcp: Access ports and units with container_of in sysfs code [SCSI] zfcp: Remove suspend callback [SCSI] zfcp: Remove global config_mutex [SCSI] zfcp: Replace local reference counting with common kref ...
2009-12-08Merge git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/sysctl-2.6Linus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/sysctl-2.6: (43 commits) security/tomoyo: Remove now unnecessary handling of security_sysctl. security/tomoyo: Add a special case to handle accesses through the internal proc mount. sysctl: Drop & in front of every proc_handler. sysctl: Remove CTL_NONE and CTL_UNNUMBERED sysctl: kill dead ctl_handler definitions. sysctl: Remove the last of the generic binary sysctl support sysctl net: Remove unused binary sysctl code sysctl security/tomoyo: Don't look at ctl_name sysctl arm: Remove binary sysctl support sysctl x86: Remove dead binary sysctl support sysctl sh: Remove dead binary sysctl support sysctl powerpc: Remove dead binary sysctl support sysctl ia64: Remove dead binary sysctl support sysctl s390: Remove dead sysctl binary support sysctl frv: Remove dead binary sysctl support sysctl mips/lasat: Remove dead binary sysctl support sysctl drivers: Remove dead binary sysctl support sysctl crypto: Remove dead binary sysctl support sysctl security/keys: Remove dead binary sysctl support sysctl kernel: Remove binary sysctl logic ...
2009-12-07Merge branch 'for-next' into for-linusJiri Kosina
Conflicts: kernel/irq/chip.c
2009-12-04[SCSI] scsi_dh: Change the scsidh_activate interface to be asynchronousChandra Seetharaman
Make scsi_dh_activate() function asynchronous, by taking in two additional parameters, one is the callback function and the other is the data to call the callback function with. Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
2009-12-01md: revert incorrect fix for read error handling in raid1.NeilBrown
commit 4706b349f was a forward port of a fix that was needed for SLES10. But in fact it is not needed in mainline because the earlier commit dd00a99e7a fixes the same problem in a better way. Further, this commit introduces a bug in the way it interacts with the automatic read-error-correction. If, after a read error is successfully corrected, the same disk is chosen to re-read - the re-read won't be attempted but an error will be returned instead. After reverting that commit, there is the possibility that a read error on a read-only array (where read errors cannot be corrected as that requires a write) will repeatedly read the same device and continue to get an error. So in the "Array is readonly" case, fail the drive immediately on a read error. Signed-off-by: NeilBrown <neilb@suse.de> Cc: stable@kernel.org
2009-11-18sysctl: Drop & in front of every proc_handler.Eric W. Biederman
For consistency drop & in front of every proc_handler. Explicity taking the address is unnecessary and it prevents optimizations like stubbing the proc_handlers to NULL. Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Joe Perches <joe@perches.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2009-11-17Merge commit 'v2.6.32-rc7'Eric W. Biederman
Resolve the conflict between v2.6.32-rc7 where dn_def_dev_handler gets a small bug fix and the sysctl tree where I am removing all sysctl strategy routines.
2009-11-13md/raid5: Allow dirty-degraded arrays to be assembled when only party is ↵NeilBrown
degraded. Normally is it not safe to allow a raid5 that is both dirty and degraded to be assembled without explicit request from that admin, as it can cause hidden data corruption. This is because 'dirty' means that the parity cannot be trusted, and 'degraded' means that the parity needs to be used. However, if the device that is missing contains only parity, then there is no issue and assembly can continue. This particularly applies when a RAID5 is being converted to a RAID6 and there is an unclean shutdown while the conversion is happening. So check for whether the degraded space only contains parity, and in that case, allow the assembly. Signed-off-by: NeilBrown <neilb@suse.de>
2009-11-13Don't unconditionally set in_sync on newly added device in raid5_reshapeNeilBrown
When a reshape finds that it can add spare devices into the array, those devices might already be 'in_sync' if they are beyond the old size of the array, or they might not if they are within the array. The first case happens when we change an N-drive RAID5 to an N+1-drive RAID5. The second happens when we convert an N-drive RAID5 to an N+1-drive RAID6. So set the flag more carefully. Also, ->recovery_offset is only meaningful when the flag is clear, so only set it in that case. This change needs the preceding two to ensure that the non-in_sync device doesn't get evicted from the array when it is stopped, in the case where v0.90 metadata is used. Signed-off-by: NeilBrown <neilb@suse.de>
2009-11-13md: allow v0.91 metadata to record devices as being active but not in-sync.NeilBrown
This is a combination that didn't really make sense before. However when a reshape is converting e.g. raid5 -> raid6, the extra device is not fully in-sync, but is certainly active and contains important data. So allow that start to be meaningful and in particular get the 'recovery_offset' value (which is needed for any non-in-sync active device) from the reshape_position. Signed-off-by: NeilBrown <neilb@suse.de>
2009-11-12sysctl drivers: Remove dead binary sysctl supportEric W. Biederman
Now that sys_sysctl is a wrapper around /proc/sys all of the binary sysctl support elsewhere in the tree is dead code. Cc: Jens Axboe <axboe@kernel.dk> Cc: Corey Minyard <minyard@acm.org> Cc: Greg Kroah-Hartman <gregkh@suse.de> Cc: Matt Mackall <mpm@selenic.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Neil Brown <neilb@suse.de> Cc: "James E.J. Bottomley" <James.Bottomley@suse.de> Acked-by: Clemens Ladisch <clemens@ladisch.de> for drivers/char/hpet.c Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2009-11-12md: factor out updating of 'recovery_offset'.NeilBrown
Each device has its own 'recovery_offset' showing how far recovery has progressed on the device. As the only real significance of this is that fact that it can be stored in the metadata and recovered at restart, and as only 1.x metadata can do this, we were only updating 'recovery_offset' to 'curr_resync_completed' when updating v1.x metadata. But this is wrong, and we will shortly make limited use of this field in v0.90 metadata. So move the update into common code. Signed-off-by: NeilBrown <neilb@suse.de>
2009-11-09tree-wide: fix a very frequent spelling mistakeDirk Hohndel
something-bility is spelled as something-blity so a grep for 'blit' would find these lines this is so trivial that I didn't split it by subsystem / copy additional maintainers - all changes are to comments The only purpose is to get fewer false positives when grepping around the kernel sources. Signed-off-by: Dirk Hohndel <hohndel@infradead.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2009-11-06md/raid5: make sure curr_sync_completes is uptodate when reshape startsNeilBrown
This value is visible through sysfs and is used by mdadm when it manages a reshape (backing up data that is about to be rearranged). So it is important that it is always correct. Current it does not get updated properly when a reshape starts which can cause problems when assembling an array that is in the middle of being reshaped. This is suitable for 2.6.31.y stable kernels. Cc: stable@kernel.org Signed-off-by: NeilBrown <neilb@suse.de>
2009-11-06md: don't clear endpoint for resync when resync is interrupted.NeilBrown
If a 'sync_max' has been set (via sysfs), it is wrong to clear it until a resync (or reshape or recovery ...) actually reached that point. So if a resync is interrupted (e.g. by device failure), leave 'resync_max' unchanged. This is particularly important for 'reshape' operations that do not change the size of the array. For such operations mdadm needs to monitor the reshape taking rolling backups of the section being reshaped. If resync_max gets cleared, the reshape can get ahead of mdadm and then the backups that mdadm creates are useless. This is suitable for 2.6.31.y stable kernels. Cc: stable@kernel.org Signed-off-by: NeilBrown <neilb@suse.de>
2009-10-31Merge branch 'for-linus' of git://neil.brown.name/mdLinus Torvalds
* 'for-linus' of git://neil.brown.name/md: async_tx: fix asynchronous raid6 recovery for ddf layouts async_pq: rename scribble page async_pq: kill a stray dma_map() call and other cleanups md/raid6: kill a gcc-4.0.1 'uninitialized variable' warning raid6/async_tx: handle holes in block list in async_syndrome_val md/async: don't pass a memory pointer as a page pointer. md: Fix handling of raid5 array which is being reshaped to fewer devices. md: fix problems with RAID6 calculations for DDF. md/raid456: downlevel multicore operations to raid_run_ops md: drivers/md/unroll.pl replaced with awk analog md: remove clumsy usage of do_sync_mapping_range from bitmap code md: raid1/raid10: handle allocation errors during array setup. md/raid5: initialize conf->device_lock earlier md/raid1/raid10: add a cond_resched Revert "md: do not progress the resync process if the stripe was blocked"
2009-10-19md/raid6: kill a gcc-4.0.1 'uninitialized variable' warningDan Williams
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2009-10-16dm snapshot: allow chunk size to be less than page sizeMikulas Patocka
Allow the snapshot chunk size to be smaller than the page size The code is now capable of handling this due to some previous fixes and enhancements. As the page size varies between computers, prior to this patch, the chunk size of a snapshot dictated which machines could read it: Snapshots created on one machine might not be readable on another. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm snapshot: use unsigned integer chunk sizeMikulas Patocka
Use unsigned integer chunk size. Maximum chunk size is 512kB, there won't ever be need to use 4GB chunk size, so the number can be 32-bit. This fixes compiler failure on 32-bit systems with large block devices. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm snapshot: lock snapshot while supplying statusMikulas Patocka
This patch locks the snapshot when returning status. It fixes a race when it could return an invalid number of free chunks if someone was simultaneously modifying it. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm exception store: fix failed set_chunk_size error pathMikulas Patocka
Properly close the device if failing because of an invalid chunk size. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm snapshot: require non zero chunk size by end of ctrMikulas Patocka
If we are creating snapshot with memory-stored exception store, fail if the user didn't specify chunk size. Zero chunk size would probably crash a lot of places in the rest of snapshot code. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Jonathan Brassow <jbrassow@redhat.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm: dec_pending needs locking to save error valueKiyoshi Ueda
Multiple instances of dec_pending() can run concurrently so a lock is needed when it saves the first error code. I have never experienced actual problem without locking and just found this during code inspection while implementing the barrier support patch for request-based dm. This patch adds the locking. I've done compile, boot and basic I/O testings. Cc: stable@kernel.org Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm: add missing del_gendisk to alloc_dev error pathZdenek Kabelac
Add missing del_gendisk() to error path when creation of workqueue fails. Otherwice there is a resource leak and following warning is shown: WARNING: at fs/sysfs/dir.c:487 sysfs_add_one+0xc5/0x160() sysfs: cannot create duplicate filename '/devices/virtual/block/dm-0' Cc: stable@kernel.org Signed-off-by: Zdenek Kabelac <zkabelac@redhat.com> Reviewed-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm log: userspace fix incorrect luid cast in userspace_ctrAndrew Morton
mips: drivers/md/dm-log-userspace-base.c: In function `userspace_ctr': drivers/md/dm-log-userspace-base.c:159: warning: cast from pointer to integer of different size Cc: stable@kernel.org Cc: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm snapshot: free exception store on init failureJonathan Brassow
While initializing the snapshot module, if we fail to register the snapshot target then we must back-out the exception store module initialization. Cc: stable@kernel.org Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16dm snapshot: sort by chunk size to fix raceMikulas Patocka
Avoid a race causing corruption when snapshots of the same origin have different chunk sizes by sorting the internal list of snapshots by chunk size, largest first. https://bugzilla.redhat.com/show_bug.cgi?id=182659 For example, let's have two snapshots with different chunk sizes. The first snapshot (1) has small chunk size and the second snapshot (2) has large chunk size. Let's have chunks A, B, C in these snapshots: snapshot1: ====A==== ====B==== snapshot2: ==========C========== (Chunk size is a power of 2. Chunks are aligned.) A write to the origin at a position within A and C comes along. It triggers reallocation of A, then reallocation of C and links them together using A as the 'primary' exception. Then another write to the origin comes along at a position within B and C. It creates pending exception for B. C already has a reallocation in progress and it already has a primary exception (A), so nothing is done to it: B and C are not linked. If the reallocation of B finishes before the reallocation of C, because there is no link with the pending exception for C it does not know to wait for it and, the second write is dispatched to the origin and causes data corruption in the chunk C in snapshot2. To avoid this situation, we maintain snapshots sorted in descending order of chunk size. This leads to a guaranteed ordering on the links between the pending exceptions and avoids the problem explained above - both A and B now get linked to C. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>