On Wed, Nov 01, 2017 at 12:42:18PM +0200, Nikolay Borisov wrote: > > > On 1.11.2017 11:46, Roman Mamedov wrote: > > On Wed, 1 Nov 2017 11:32:18 +0200 > > Nikolay Borisov <nborisov@xxxxxxxx> wrote: > > > >> Fallocating a file in btrfs goes through several stages. The one before actually > >> inserting the fallocated extents is to create a qgroup reservation, covering > >> the desired range. To this end there is a loop in btrfs_fallocate which checks > >> to see if there are holes in the fallocated range or !PREALLOC extents past EOF > >> and if so create qgroup reservations for them. Unfortunately, the main condition > >> of the loop is burried right at the end of its body rather than in the actual > >> while statement which makes it non-obvious. Fix this by moving the condition > >> in the while statement where it belongs. No functional changes. > > > > If it turns out that "cur_offset >= alloc_end" from the get go, previously the > > loop body would be entered and executed once. With this change, it will not > > anymore. > > Good point, however this cannot happen, because for this to happen then > the following 2 expression need to be equal: > > alloc_start = round_down(offset, blocksize); > alloc_end = round_up(offset + len, blocksize); > > However, len is guaranteed to be > 0 due to a check in vfs_fallocate so > those can't really be equal. Agreed, and Reviewed-by: David Sterba <dsterba@xxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
