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authorJeff Moyer <jmoyer@redhat.com>2006-02-03 03:04:27 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-03 08:32:07 -0800
commit35dc8161d0a6fa5e654bcb3d6240acc9ecb0a259 (patch)
tree0c688ffc3adc127f5cf9f35ff93e6072e1f42438 /fs/direct-io.c
parent835417967c10b6dfaffdffddba59196196e5d431 (diff)
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[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.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 30dbbd1df51..848044af7e1 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;