| Message ID | 1525682525-1424-2-git-send-email-robbieko@synology.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 7.05.2018 11:42, robbieko wrote: > From: Robbie Ko <robbieko@synology.com> > > [BUG] > fm_mapped_extents is not correct when fm_extent_count is 0 > Like: > # mount /dev/vdb5 /mnt/btrfs > # dd if=/dev/zero bs=16K count=4 oflag=dsync of=/mnt/btrfs/file > # xfs_io -c "fiemap -v" /mnt/btrfs/file > /mnt/btrfs/file: > EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS > 0: [0..127]: 25088..25215 128 0x1 > > When user space wants to get the number of file extents, > set fm_extent_count to 0 to run fiemap and then read fm_mapped_extents. "it sets fm_extent_count to 0.... and then reads fm_mapped_extents" > > In the above example, fiemap will return with fm_mapped_extents set to 4, > but it should be 1 since there's only one entry in the output. > > [REASON] > The problem seems to be that disko is only set if > fieinfo->fi_extents_max is set. And this member is initialized, in the > generic ioctl_fiemap function, to the value of used-passed ^^^^ user-passed > fm_extent_count. So when the user passes 0 then fi_extent_max is also > set to zero and this causes btrfs to not initialize disko at all. > Eventually this leads emit_fiemap_extent being called with a bogus > 'phys' argument preventing proper fiemap entries merging. > > [FIX] > Move the disko initialization earlier in extent_fiemap making it > independent of user-passed arguments, allowing emit_fiemap_extent to > properly handle consecutive extent entries. > > Signed-off-by: Robbie Ko <robbieko@synology.com> Only a couple of minor nits w.r.t the changelog but I guess David can fix this on the go. In any case : Reviewed-by: Nikolay Borisov <nborisov@suse.com> > --- > V2: > fix comments. > > fs/btrfs/extent_io.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index 012d638..066b6df 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -4567,7 +4567,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > offset_in_extent = em_start - em->start; > em_end = extent_map_end(em); > em_len = em_end - em_start; > - disko = 0; > + disko = em->block_start + offset_in_extent; > flags = 0; > > /* > @@ -4590,8 +4590,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > u64 bytenr = em->block_start - > (em->start - em->orig_start); > > - disko = em->block_start + offset_in_extent; > - > /* > * As btrfs supports shared space, this information > * can be exported to userspace tools via > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 012d638..066b6df 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4567,7 +4567,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, offset_in_extent = em_start - em->start; em_end = extent_map_end(em); em_len = em_end - em_start; - disko = 0; + disko = em->block_start + offset_in_extent; flags = 0; /* @@ -4590,8 +4590,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, u64 bytenr = em->block_start - (em->start - em->orig_start); - disko = em->block_start + offset_in_extent; - /* * As btrfs supports shared space, this information * can be exported to userspace tools via