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authorJeff Moyer <jmoyer@redhat.com>2012-05-11 16:34:10 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-06-01 15:12:52 +0800
commit37a8457773c266cdb77fcddec008cd73e81786be (patch)
tree2a7de7c0b6f998d9da800e68b0a22b0e5d468048 /fs/buffer.c
parent19e40444eb3a1fddeb274c25951bdcace4315d6a (diff)
downloadlwn-37a8457773c266cdb77fcddec008cd73e81786be.tar.gz
lwn-37a8457773c266cdb77fcddec008cd73e81786be.zip
block: don't mark buffers beyond end of disk as mapped
commit 080399aaaf3531f5b8761ec0ac30ff98891e8686 upstream. Hi, We have a bug report open where a squashfs image mounted on ppc64 would exhibit errors due to trying to read beyond the end of the disk. It can easily be reproduced by doing the following: [root@ibm-p750e-02-lp3 ~]# ls -l install.img -rw-r--r-- 1 root root 142032896 Apr 30 16:46 install.img [root@ibm-p750e-02-lp3 ~]# mount -o loop ./install.img /mnt/test [root@ibm-p750e-02-lp3 ~]# dd if=/dev/loop0 of=/dev/null dd: reading `/dev/loop0': Input/output error 277376+0 records in 277376+0 records out 142016512 bytes (142 MB) copied, 0.9465 s, 150 MB/s In dmesg, you'll find the following: squashfs: version 4.0 (2009/01/31) Phillip Lougher [ 43.106012] attempt to access beyond end of device [ 43.106029] loop0: rw=0, want=277410, limit=277408 [ 43.106039] Buffer I/O error on device loop0, logical block 138704 [ 43.106053] attempt to access beyond end of device [ 43.106057] loop0: rw=0, want=277412, limit=277408 [ 43.106061] Buffer I/O error on device loop0, logical block 138705 [ 43.106066] attempt to access beyond end of device [ 43.106070] loop0: rw=0, want=277414, limit=277408 [ 43.106073] Buffer I/O error on device loop0, logical block 138706 [ 43.106078] attempt to access beyond end of device [ 43.106081] loop0: rw=0, want=277416, limit=277408 [ 43.106085] Buffer I/O error on device loop0, logical block 138707 [ 43.106089] attempt to access beyond end of device [ 43.106093] loop0: rw=0, want=277418, limit=277408 [ 43.106096] Buffer I/O error on device loop0, logical block 138708 [ 43.106101] attempt to access beyond end of device [ 43.106104] loop0: rw=0, want=277420, limit=277408 [ 43.106108] Buffer I/O error on device loop0, logical block 138709 [ 43.106112] attempt to access beyond end of device [ 43.106116] loop0: rw=0, want=277422, limit=277408 [ 43.106120] Buffer I/O error on device loop0, logical block 138710 [ 43.106124] attempt to access beyond end of device [ 43.106128] loop0: rw=0, want=277424, limit=277408 [ 43.106131] Buffer I/O error on device loop0, logical block 138711 [ 43.106135] attempt to access beyond end of device [ 43.106139] loop0: rw=0, want=277426, limit=277408 [ 43.106143] Buffer I/O error on device loop0, logical block 138712 [ 43.106147] attempt to access beyond end of device [ 43.106151] loop0: rw=0, want=277428, limit=277408 [ 43.106154] Buffer I/O error on device loop0, logical block 138713 [ 43.106158] attempt to access beyond end of device [ 43.106162] loop0: rw=0, want=277430, limit=277408 [ 43.106166] attempt to access beyond end of device [ 43.106169] loop0: rw=0, want=277432, limit=277408 ... [ 43.106307] attempt to access beyond end of device [ 43.106311] loop0: rw=0, want=277470, limit=2774 Squashfs manages to read in the end block(s) of the disk during the mount operation. Then, when dd reads the block device, it leads to block_read_full_page being called with buffers that are beyond end of disk, but are marked as mapped. Thus, it would end up submitting read I/O against them, resulting in the errors mentioned above. I fixed the problem by modifying init_page_buffers to only set the buffer mapped if it fell inside of i_size. Cheers, Jeff Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Acked-by: Nick Piggin <npiggin@kernel.dk> -- Changes from v1->v2: re-used max_block, as suggested by Nick Piggin. Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/buffer.c')
-rw-r--r--fs/buffer.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 1a80b048ade8..330cbce11413 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -968,6 +968,7 @@ init_page_buffers(struct page *page, struct block_device *bdev,
struct buffer_head *head = page_buffers(page);
struct buffer_head *bh = head;
int uptodate = PageUptodate(page);
+ sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode));
do {
if (!buffer_mapped(bh)) {
@@ -976,7 +977,8 @@ init_page_buffers(struct page *page, struct block_device *bdev,
bh->b_blocknr = block;
if (uptodate)
set_buffer_uptodate(bh);
- set_buffer_mapped(bh);
+ if (block < end_block)
+ set_buffer_mapped(bh);
}
block++;
bh = bh->b_this_page;