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authorFilipe Manana <fdmanana@suse.com>2014-08-29 20:54:26 +0100
committerChris Mason <clm@fb.com>2014-09-02 16:46:05 -0700
commitdac5705cad20070a70bb028ca52e1f0bc157b42d (patch)
treea821d66c9ccb23f370192861bce9c94d9ceb92b7 /fs
parentd9f85963e3f7f5582552fdae54a2b89d6c62daf5 (diff)
downloadlinux-next-dac5705cad20070a70bb028ca52e1f0bc157b42d.tar.gz
Btrfs: fix crash while doing a ranged fsync
While doing a ranged fsync, that is, one whose range doesn't cover the whole possible file range (0 to LLONG_MAX), we can crash under certain circumstances with a trace like the following: [41074.641913] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC (...) [41074.642692] CPU: 0 PID: 24580 Comm: fsx Not tainted 3.16.0-fdm-btrfs-next-45+ #1 (...) [41074.643886] RIP: 0010:[<ffffffffa01ecc99>] [<ffffffffa01ecc99>] btrfs_ordered_update_i_size+0x279/0x2b0 [btrfs] (...) [41074.644919] Stack: (...) [41074.644919] Call Trace: [41074.644919] [<ffffffffa01db531>] btrfs_truncate_inode_items+0x3f1/0xa10 [btrfs] [41074.644919] [<ffffffffa01eb54f>] ? btrfs_get_logged_extents+0x4f/0x80 [btrfs] [41074.644919] [<ffffffffa02137a9>] btrfs_log_inode+0x2f9/0x970 [btrfs] [41074.644919] [<ffffffff81090875>] ? sched_clock_local+0x25/0xa0 [41074.644919] [<ffffffff8164a55e>] ? mutex_unlock+0xe/0x10 [41074.644919] [<ffffffff810af51d>] ? trace_hardirqs_on+0xd/0x10 [41074.644919] [<ffffffffa0214b4f>] btrfs_log_inode_parent+0x1ef/0x560 [btrfs] [41074.644919] [<ffffffff811d0c55>] ? dget_parent+0x5/0x180 [41074.644919] [<ffffffffa0215d11>] btrfs_log_dentry_safe+0x51/0x80 [btrfs] [41074.644919] [<ffffffffa01e2d1a>] btrfs_sync_file+0x1ba/0x3e0 [btrfs] [41074.644919] [<ffffffff811eda6b>] vfs_fsync_range+0x1b/0x30 (...) The necessary conditions that lead to such crash are: * an incremental fsync (when the inode doesn't have the BTRFS_INODE_NEEDS_FULL_SYNC flag set) happened for our file and it logged a file extent item ending at offset X; * the file got the flag BTRFS_INODE_NEEDS_FULL_SYNC set in its inode, due to a file truncate operation that reduces the file to a size smaller than X; * a ranged fsync call happens (via an msync for example), with a range that doesn't cover the whole file and the end of this range, lets call it Y, is smaller than X; * btrfs_log_inode, sees the flag BTRFS_INODE_NEEDS_FULL_SYNC set and calls btrfs_truncate_inode_items() to remove all items from the log tree that are associated with our file; * btrfs_truncate_inode_items() removes all of the inode's items, and the lowest file extent item it removed is the one ending at offset X, where X > 0 and X > Y - before returning, it calls btrfs_ordered_update_i_size() with an offset parameter set to X; * btrfs_ordered_update_i_size() sees that X is greater then the current ordered size (btrfs_inode's disk_i_size) and then it assumes there can't be any ongoing ordered operation with a range covering the offset X, calling a BUG_ON() if such ordered operation exists. This assumption is made because the disk_i_size is only increased after the corresponding file extent item is added to the btree (btrfs_finish_ordered_io); * But because our fsync covers only a limited range, such an ordered extent might exist, and our fsync callback (btrfs_sync_file) doesn't wait for such ordered extent to finish when calling btrfs_wait_ordered_range(); And then by the time btrfs_ordered_update_i_size() is called, via: btrfs_sync_file() -> btrfs_log_dentry_safe() -> btrfs_log_inode_parent() -> btrfs_log_inode() -> btrfs_truncate_inode_items() -> btrfs_ordered_update_i_size() We hit the BUG_ON(), which could never happen if the fsync range covered the whole possible file range (0 to LLONG_MAX), as we would wait for all ordered extents to finish before calling btrfs_truncate_inode_items(). So just don't call btrfs_ordered_update_i_size() if we're removing the inode's items from a log tree, which isn't supposed to change the in memory inode's disk_i_size. Issue found while running xfstests/generic/127 (happens very rarely for me), more specifically via the fsx calls that use memory mapped IO (and issue msync calls). Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/inode.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 7313571e1860..88823f4ca451 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4248,7 +4248,8 @@ out:
btrfs_abort_transaction(trans, root, ret);
}
error:
- if (last_size != (u64)-1)
+ if (last_size != (u64)-1 &&
+ root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
btrfs_ordered_update_i_size(inode, last_size, NULL);
btrfs_free_path(path);
return err;