From a66d636385d621e98a915233250356c394a437de Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 22 Mar 2012 05:15:12 +0000 Subject: xfs: fix fstrim offset calculations xfs_ioc_fstrim() doesn't treat the incoming offset and length correctly. It treats them as a filesystem block address, rather than a disk address. This is wrong because the range passed in is a linear representation, while the filesystem block address notation is a sparse representation. Hence we cannot convert the range direct to filesystem block units and then use that for calculating the range to trim. While this sounds dangerous, the problem is limited to calculating what AGs need to be trimmed. The code that calcuates the actual ranges to trim gets the right result (i.e. only ever discards free space), even though it uses the wrong ranges to limit what is trimmed. Hence this is not a bug that endangers user data. Fix this by treating the range as a disk address range and use the appropriate functions to convert the range into the desired formats for calculations. Further, fix the first free extent lookup (the longest) to actually find the largest free extent. Currently this lookup uses a <= lookup, which results in finding the extent to the left of the largest because we can never get an exact match on the largest extent. This is due to the fact that while we know it's size, we don't know it's location and so the exact match fails and we move one record to the left to get the next largest extent. Instead, use a >= search so that the lookup returns the largest extent regardless of the fact we don't get an exact match on it. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Ben Myers --- fs/xfs/xfs_alloc.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'fs/xfs/xfs_alloc.h') diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h index ab5d0fd2f535..3a7e7d8f8ded 100644 --- a/fs/xfs/xfs_alloc.h +++ b/fs/xfs/xfs_alloc.h @@ -248,6 +248,13 @@ xfs_alloc_lookup_le( xfs_extlen_t len, /* length of extent */ int *stat); /* success/failure */ +int /* error */ +xfs_alloc_lookup_ge( + struct xfs_btree_cur *cur, /* btree cursor */ + xfs_agblock_t bno, /* starting block of extent */ + xfs_extlen_t len, /* length of extent */ + int *stat); /* success/failure */ + int /* error */ xfs_alloc_get_rec( struct xfs_btree_cur *cur, /* btree cursor */ -- cgit v1.2.3