| Message ID | 1240859143-31122-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com |
|---|---|
| State | Superseded, archived |
| Headers | show |
Aneesh Kumar K.V wrote: > We need to mark the buffer_head mapping prealloc space > as new during write_begin. Otherwise we don't zero out the > page cache content properly for a partial write. This will > cause file corruption with preallocation. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > > --- > fs/ext4/inode.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index c6bd6ce..c7251ec 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -2323,6 +2323,8 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, > set_buffer_delay(bh_result); > } else if (ret > 0) { > bh_result->b_size = (ret << inode->i_blkbits); > + if (buffer_unwritten(bh_result)) > + set_buffer_new(bh_result); > ret = 0; > } > Hm, yep, that sure does break things. For some future regression test: [root@inode tmp]# /root/fallocate -l 8k testfile [root@inode tmp]# dd if=/dev/zero of=testfile bs=1 count=10 conv=notrunc 10+0 records in 10+0 records out 10 bytes (10 B) copied, 5.1491e-05 s, 194 kB/s [root@inode tmp]# hexdump -C testfile <much garbage ensues> This looks pretty reasonable; Aneesh & I talked online and found that xfs has a somewhat similar fix: commit 549054afadae44889c0b40d4c3bfb0207b98d5a0 Author: David Chinner <dgc@sgi.com> Date: Sat Feb 10 18:36:35 2007 +1100 [XFS] Fix sub-block zeroing for buffered writes into unwritten extents. When writing less than a filesystem block of data into an unwritten extent via buffered I/O, __xfs_get_blocks fails to set the buffer new flag. As a result, the generic code will not zero either edge of the block resulting in garbage being written to disk either side of the real data. Set the buffer new state on bufferd writes to unwritten extents to ensure that zeroing occurs. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" 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/ext4/inode.c b/fs/ext4/inode.c index c6bd6ce..c7251ec 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2323,6 +2323,8 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, set_buffer_delay(bh_result); } else if (ret > 0) { bh_result->b_size = (ret << inode->i_blkbits); + if (buffer_unwritten(bh_result)) + set_buffer_new(bh_result); ret = 0; }
We need to mark the buffer_head mapping prealloc space as new during write_begin. Otherwise we don't zero out the page cache content properly for a partial write. This will cause file corruption with preallocation. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> --- fs/ext4/inode.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)