diff options
| author | Jeff Moyer <jmoyer@redhat.com> | 2006-02-03 03:04:27 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-03 08:32:07 -0800 |
| commit | 35dc8161d0a6fa5e654bcb3d6240acc9ecb0a259 (patch) | |
| tree | 0c688ffc3adc127f5cf9f35ff93e6072e1f42438 /fs/direct-io.c | |
| parent | 835417967c10b6dfaffdffddba59196196e5d431 (diff) | |
[PATCH] fix O_DIRECT read of last block in a sparse file
Currently, if you open a file O_DIRECT, truncate it to a size that is not a
multiple of the disk block size, and then try to read the last block in the
file, the read will return 0. The problem is in do_direct_IO, here:
/* Handle holes */
if (!buffer_mapped(map_bh)) {
char *kaddr;
...
if (dio->block_in_file >=
i_size_read(dio->inode)>>blkbits) {
/* We hit eof */
page_cache_release(page);
goto out;
}
We shift off any remaining bytes in the final block of the I/O, resulting
in a 0-sized read. I've attached a patch that fixes this. I'm not happy
about how ugly the math is getting, so suggestions are more than welcome.
I've tested this with a simple program that performs the steps outlined for
reproducing the problem above. Without the patch, we get a 0-sized result
from read. With the patch, we get the correct return value from the short
read.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Joel Becker <Joel.Becker@oracle.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/direct-io.c')
| -rw-r--r-- | fs/direct-io.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c index 30dbbd1df511..848044af7e16 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -857,6 +857,7 @@ do_holes: /* Handle holes */ if (!buffer_mapped(map_bh)) { char *kaddr; + loff_t i_size_aligned; /* AKPM: eargh, -ENOTBLK is a hack */ if (dio->rw == WRITE) { @@ -864,8 +865,14 @@ do_holes: return -ENOTBLK; } + /* + * Be sure to account for a partial block as the + * last block in the file + */ + i_size_aligned = ALIGN(i_size_read(dio->inode), + 1 << blkbits); if (dio->block_in_file >= - i_size_read(dio->inode)>>blkbits) { + i_size_aligned >> blkbits) { /* We hit eof */ page_cache_release(page); goto out; |