BMC/Intel-BMC/linux.git/fs/btrfs, branch dev-4.17

Btrfs: fix file data corruption after cloning a range and fsync

2018-08-09T10:15:12+00:00

commit bd3599a0e142cd73edd3b6801068ac3f48ac771a upstream. When we clone a range into a file we can end up dropping existing extent maps (or trimming them) and replacing them with new ones if the range to be cloned overlaps with a range in the destination inode. When that happens we add the new extent maps to the list of modified extents in the inode's extent map tree, so that a "fast" fsync (the flag BTRFS_INODE_NEEDS_FULL_SYNC not set in the inode) will see the extent maps and log corresponding extent items. However, at the end of range cloning operation we do truncate all the pages in the affected range (in order to ensure future reads will not get stale data). Sometimes this truncation will release the corresponding extent maps besides the pages from the page cache. If this happens, then a "fast" fsync operation will miss logging some extent items, because it relies exclusively on the extent maps being present in the inode's extent tree, leading to data loss/corruption if the fsync ends up using the same transaction used by the clone operation (that transaction was not committed in the meanwhile). An extent map is released through the callback btrfs_invalidatepage(), which gets called by truncate_inode_pages_range(), and it calls __btrfs_releasepage(). The later ends up calling try_release_extent_mapping() which will release the extent map if some conditions are met, like the file size being greater than 16Mb, gfp flags allow blocking and the range not being locked (which is the case during the clone operation) nor being the extent map flagged as pinned (also the case for cloning). The following example, turned into a test for fstests, reproduces the issue: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ xfs_io -f -c "pwrite -S 0x18 9000K 6908K" /mnt/foo $ xfs_io -f -c "pwrite -S 0x20 2572K 156K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar # reflink destination offset corresponds to the size of file bar, # 2728Kb minus 4Kb. $ xfs_io -c ""reflink ${SCRATCH_MNT}/foo 0 2724K 15908K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar $ md5sum /mnt/bar 95a95813a8c2abc9aa75a6c2914a077e /mnt/bar $ mount /dev/sdb /mnt $ md5sum /mnt/bar 207fd8d0b161be8a84b945f0df8d5f8d /mnt/bar # digest should be 95a95813a8c2abc9aa75a6c2914a077e like before the # power failure In the above example, the destination offset of the clone operation corresponds to the size of the "bar" file minus 4Kb. So during the clone operation, the extent map covering the range from 2572Kb to 2728Kb gets trimmed so that it ends at offset 2724Kb, and a new extent map covering the range from 2724Kb to 11724Kb is created. So at the end of the clone operation when we ask to truncate the pages in the range from 2724Kb to 2724Kb + 15908Kb, the page invalidation callback ends up removing the new extent map (through try_release_extent_mapping()) when the page at offset 2724Kb is passed to that callback. Fix this by setting the bit BTRFS_INODE_NEEDS_FULL_SYNC whenever an extent map is removed at try_release_extent_mapping(), forcing the next fsync to search for modified extents in the fs/subvolume tree instead of relying on the presence of extent maps in memory. This way we can continue doing a "fast" fsync if the destination range of a clone operation does not overlap with an existing range or if any of the criteria necessary to remove an extent map at try_release_extent_mapping() is not met (file size not bigger then 16Mb or gfp flags do not allow blocking). CC: stable@vger.kernel.org # 3.16+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Sudip Mukherjee Signed-off-by: Greg Kroah-Hartman

btrfs: qgroup: Finish rescan when hit the last leaf of extent tree

2018-08-03T05:47:43+00:00

[ Upstream commit ff3d27a048d926b3920ccdb75d98788c567cae0d ] Under the following case, qgroup rescan can double account cowed tree blocks: In this case, extent tree only has one tree block. - | transid=5 last committed=4 | btrfs_qgroup_rescan_worker() | |- btrfs_start_transaction() | | transid = 5 | |- qgroup_rescan_leaf() | |- btrfs_search_slot_for_read() on extent tree | Get the only extent tree block from commit root (transid = 4). | Scan it, set qgroup_rescan_progress to the last | EXTENT/META_ITEM + 1 | now qgroup_rescan_progress = A + 1. | | fs tree get CoWed, new tree block is at A + 16K | transid 5 get committed - | transid=6 last committed=5 | btrfs_qgroup_rescan_worker() | btrfs_qgroup_rescan_worker() | |- btrfs_start_transaction() | | transid = 5 | |- qgroup_rescan_leaf() | |- btrfs_search_slot_for_read() on extent tree | Get the only extent tree block from commit root (transid = 5). | scan it using qgroup_rescan_progress (A + 1). | found new tree block beyong A, and it's fs tree block, | account it to increase qgroup numbers. - In above case, tree block A, and tree block A + 16K get accounted twice, while qgroup rescan should stop when it already reach the last leaf, other than continue using its qgroup_rescan_progress. Such case could happen by just looping btrfs/017 and with some possibility it can hit such double qgroup accounting problem. Fix it by checking the path to determine if we should finish qgroup rescan, other than relying on next loop to exit. Reported-by: Nikolay Borisov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: add barriers to btrfs_sync_log before log_commit_wait wakeups

2018-08-03T05:47:43+00:00

[ Upstream commit 3d3a2e610ea5e7c6d4f9481ecce5d8e2d8317843 ] Currently the code assumes that there's an implied barrier by the sequence of code preceding the wakeup, namely the mutex unlock. As Nikolay pointed out: I think this is wrong (not your code) but the original assumption that the RELEASE semantics provided by mutex_unlock is sufficient. According to memory-barriers.txt: Section 'LOCK ACQUISITION FUNCTIONS' states: (2) RELEASE operation implication: Memory operations issued before the RELEASE will be completed before the RELEASE operation has completed. Memory operations issued after the RELEASE *may* be completed before the RELEASE operation has completed. (I've bolded the may portion) The example given there: As an example, consider the following: *A = a; *B = b; ACQUIRE *C = c; *D = d; RELEASE *E = e; *F = f; The following sequence of events is acceptable: ACQUIRE, {*F,*A}, *E, {*C,*D}, *B, RELEASE So if we assume that *C is modifying the flag which the waitqueue is checking, and *E is the actual wakeup, then those accesses can be re-ordered... IMHO this code should be considered broken... Signed-off-by: Greg Kroah-Hartman

Btrfs: don't BUG_ON() in btrfs_truncate_inode_items()

2018-08-03T05:47:43+00:00

[ Upstream commit 0552210997badb6a60740a26ff9d976a416510f0 ] btrfs_free_extent() can fail because of ENOMEM. There's no reason to panic here, we can just abort the transaction. Fixes: f4b9aa8d3b87 ("btrfs_truncate") Reviewed-by: Nikolay Borisov Signed-off-by: Omar Sandoval Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

Btrfs: don't return ino to ino cache if inode item removal fails

2018-08-03T05:47:43+00:00

[ Upstream commit c08db7d8d295a4f3a10faaca376de011afff7950 ] In btrfs_evict_inode(), if btrfs_truncate_inode_items() fails, the inode item will still be in the tree but we still return the ino to the ino cache. That will blow up later when someone tries to allocate that ino, so don't return it to the cache. Fixes: 581bb050941b ("Btrfs: Cache free inode numbers in memory") Reviewed-by: Josef Bacik Signed-off-by: Omar Sandoval Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: balance dirty metadata pages in btrfs_finish_ordered_io

2018-08-03T05:47:41+00:00

[ Upstream commit e73e81b6d0114d4a303205a952ab2e87c44bd279 ] [Problem description and how we fix it] We should balance dirty metadata pages at the end of btrfs_finish_ordered_io, since a small, unmergeable random write can potentially produce dirty metadata which is multiple times larger than the data itself. For example, a small, unmergeable 4KiB write may produce: 16KiB dirty leaf (and possibly 16KiB dirty node) in subvolume tree 16KiB dirty leaf (and possibly 16KiB dirty node) in checksum tree 16KiB dirty leaf (and possibly 16KiB dirty node) in extent tree Although we do call balance dirty pages in write side, but in the buffered write path, most metadata are dirtied only after we reach the dirty background limit (which by far only counts dirty data pages) and wakeup the flusher thread. If there are many small, unmergeable random writes spread in a large btree, we'll find a burst of dirty pages exceeds the dirty_bytes limit after we wakeup the flusher thread - which is not what we expect. In our machine, it caused out-of-memory problem since a page cannot be dropped if it is marked dirty. Someone may worry about we may sleep in btrfs_btree_balance_dirty_nodelay, but since we do btrfs_finish_ordered_io in a separate worker, it will not stop the flusher consuming dirty pages. Also, we use different worker for metadata writeback endio, sleep in btrfs_finish_ordered_io help us throttle the size of dirty metadata pages. [Reproduce steps] To reproduce the problem, we need to do 4KiB write randomly spread in a large btree. In our 2GiB RAM machine: 1) Create 4 subvolumes. 2) Run fio on each subvolume: [global] direct=0 rw=randwrite ioengine=libaio bs=4k iodepth=16 numjobs=1 group_reporting size=128G runtime=1800 norandommap time_based randrepeat=0 3) Take snapshot on each subvolume and repeat fio on existing files. 4) Repeat step (3) until we get large btrees. In our case, by observing btrfs_root_item->bytes_used, we have 2GiB of metadata in each subvolume tree and 12GiB of metadata in extent tree. 5) Stop all fio, take snapshot again, and wait until all delayed work is completed. 6) Start all fio. Few seconds later we hit OOM when the flusher starts to work. It can be reproduced even when using nocow write. Signed-off-by: Ethan Lien Reviewed-by: David Sterba [ add comment ] Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

Btrfs: fix return value on rename exchange failure

2018-07-03T09:27:00+00:00

commit c5b4a50b74018b3677098151ec5f4fce07d5e6a0 upstream. If we failed during a rename exchange operation after starting/joining a transaction, we would end up replacing the return value, stored in the local 'ret' variable, with the return value from btrfs_end_transaction(). So this could end up returning 0 (success) to user space despite the operation having failed and aborted the transaction, because if there are multiple tasks having a reference on the transaction at the time btrfs_end_transaction() is called by the rename exchange, that function returns 0 (otherwise it returns -EIO and not the original error value). So fix this by not overwriting the return value on error after getting a transaction handle. Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT") CC: stable@vger.kernel.org # 4.9+ Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: scrub: Don't use inode pages for device replace

2018-06-25T23:51:23+00:00

commit ac0b4145d662a3b9e34085dea460fb06ede9b69b upstream. [BUG] Btrfs can create compressed extent without checksum (even though it shouldn't), and if we then try to replace device containing such extent, the result device will contain all the uncompressed data instead of the compressed one. Test case already submitted to fstests: https://patchwork.kernel.org/patch/10442353/ [CAUSE] When handling compressed extent without checksum, device replace will goe into copy_nocow_pages() function. In that function, btrfs will get all inodes referring to this data extents and then use find_or_create_page() to get pages direct from that inode. The problem here is, pages directly from inode are always uncompressed. And for compressed data extent, they mismatch with on-disk data. Thus this leads to corrupted compressed data extent written to replace device. [FIX] In this attempt, we could just remove the "optimization" branch, and let unified scrub_pages() to handle it. Although scrub_pages() won't bother reusing page cache, it will be a little slower, but it does the correct csum checking and won't cause such data corruption caused by "optimization". Note about the fix: this is the minimal fix that can be backported to older stable trees without conflicts. The whole callchain from copy_nocow_pages() can be deleted, and will be in followup patches. Fixes: ff023aac3119 ("Btrfs: add code to scrub to copy read data to another disk") CC: stable@vger.kernel.org # 4.4+ Reported-by: James Harvey Reviewed-by: James Harvey Signed-off-by: Qu Wenruo [ remove code removal, add note why ] Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: return error value if create_io_em failed in cow_file_range

2018-06-25T23:51:23+00:00

commit 090a127afa8f73e9618d4058d6755f7ec7453dd6 upstream. In cow_file_range(), create_io_em() may fail, but its return value is not recorded. Then return value may be 0 even it failed which is a wrong behavior. Let cow_file_range() return PTR_ERR(em) if create_io_em() failed. Fixes: 6f9994dbabe5 ("Btrfs: create a helper to create em for IO") CC: stable@vger.kernel.org # 4.11+ Signed-off-by: Su Yue Reviewed-by: Nikolay Borisov Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

Btrfs: fix memory and mount leak in btrfs_ioctl_rm_dev_v2()

2018-06-25T23:51:23+00:00

commit fd4e994bd1f9dc9628e168a7f619bf69f6984635 upstream. If we have invalid flags set, when we error out we must drop our writer counter and free the buffer we allocated for the arguments. This bug is trivially reproduced with the following program on 4.7+: #include #include #include #include #include #include #include #include #include #include int main(int argc, char **argv) { struct btrfs_ioctl_vol_args_v2 vol_args = { .flags = UINT64_MAX, }; int ret; int fd; if (argc != 2) { fprintf(stderr, "usage: %s PATH\n", argv[0]); return EXIT_FAILURE; } fd = open(argv[1], O_WRONLY); if (fd == -1) { perror("open"); return EXIT_FAILURE; } ret = ioctl(fd, BTRFS_IOC_RM_DEV_V2, &vol_args); if (ret == -1) perror("ioctl"); close(fd); return EXIT_SUCCESS; } When unmounting the filesystem, we'll hit the WARN_ON(mnt_get_writers(mnt)) in cleanup_mnt() and also may prevent the filesystem to be remounted read-only as the writer count will stay lifted. Fixes: 6b526ed70cf1 ("btrfs: introduce device delete by devid") CC: stable@vger.kernel.org # 4.9+ Signed-off-by: Omar Sandoval Reviewed-by: Su Yue Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman