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Commit 42cb56ae2ab67390da34906b27bedc3f2ff1393b

Authored by Jeff Layton
Committed by Al Viro
1 parent 5aa98b706e
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

vfs: change sb->s_maxbytes to a loff_t 

sb->s_maxbytes is supposed to indicate the maximum size of a file that can
exist on the filesystem.  It's declared as an unsigned long long.

Even if a filesystem has no inherent limit that prevents it from using
every bit in that unsigned long long, it's still problematic to set it to
anything larger than MAX_LFS_FILESIZE.  There are places in the kernel
that cast s_maxbytes to a signed value.  If it's set too large then this
cast makes it a negative number and generally breaks the comparison.

Change s_maxbytes to be loff_t instead.  That should help eliminate the
temptation to set it too large by making it a signed value.

Also, add a warning for couple of releases to help catch filesystems that
set s_maxbytes too large.  Eventually we can either convert this to a
BUG() or just remove it and in the hope that no one will get it wrong now
that it's a signed value.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Robert Love <rlove@google.com>
Cc: Mandeep Singh Baines <msb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Showing 2 changed files with 11 additions and 1 deletions Side-by-side Diff

... ... @@ -892,6 +892,16 @@
892 892 if (error)
893 893 goto out_sb;
894 894  
  895 + /*
  896 + * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
  897 + * but s_maxbytes was an unsigned long long for many releases. Throw
  898 + * this warning for a little while to try and catch filesystems that
  899 + * violate this rule. This warning should be either removed or
  900 + * converted to a BUG() in 2.6.34.
  901 + */
  902 + WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
  903 + "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
  904 +
895 905 mnt->mnt_mountpoint = mnt->mnt_root;
896 906 mnt->mnt_parent = mnt;
897 907 up_write(&mnt->mnt_sb->s_umount);
... ... @@ -1315,7 +1315,7 @@
1315 1315 unsigned long s_blocksize;
1316 1316 unsigned char s_blocksize_bits;
1317 1317 unsigned char s_dirt;
1318   - unsigned long long s_maxbytes; /* Max file size */
  1318 + loff_t s_maxbytes; /* Max file size */
1319 1319 struct file_system_type *s_type;
1320 1320 const struct super_operations *s_op;
1321 1321 const struct dquot_operations *dq_op;