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NFS: Fix nfs_file_llseek()

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After the BKL removal patches were applied to the rest of the NFS code, the
BKL protection in nfs_file_llseek() is no longer sufficient to ensure that
inode->i_size is read safely in generic_file_llseek_unlocked().

In order to fix the situation, we either have to replace the naked read of
inode->i_size in generic_file_llseek_unlocked() with i_size_read(), or the
whole thing needs to be executed under the inode->i_lock;
In order to avoid disrupting other filesystems, avoid touching
generic_file_llseek_unlocked() for now...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2008-09-23 17:28:35 -04:00
parent 4330ed8ed4
commit d5e66348bb
1 changed files with 7 additions and 4 deletions
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11
fs/nfs/file.c
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@ -188,13 +188,16 @@ static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
/* origin == SEEK_END => we must revalidate the cached file length */
if (origin == SEEK_END) {
struct inode *inode = filp->f_mapping->host;
int retval = nfs_revalidate_file_size(inode, filp);
if (retval < 0)
return (loff_t)retval;
}
lock_kernel(); /* BKL needed? */
loff = generic_file_llseek_unlocked(filp, offset, origin);
unlock_kernel();
spin_lock(&inode->i_lock);
loff = generic_file_llseek_unlocked(filp, offset, origin);
spin_unlock(&inode->i_lock);
} else
loff = generic_file_llseek_unlocked(filp, offset, origin);
return loff;
}