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[CIFS] Fix locking problem around some cifs uses of i_size write

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Could cause hangs on smp systems in i_size_read on a cifs inode
whose size has been previously simultaneously updated from
different processes.

Thanks to Brian Wang for some great testing/debugging on this
hard problem.

Fixes kernel bugzilla #7903

CC: Shirish Pargoankar <shirishp@us.ibm.com>
CC: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This commit is contained in:
Steve French
2007-02-26 16:46:11 +00:00
parent 9654640d0a
commit 3677db10a6
4 changed files with 82 additions and 23 deletions
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50
fs/cifs/inode.c
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@@ -143,10 +143,10 @@ int cifs_get_inode_info_unix(struct inode **pinode,
inode->i_gid = le64_to_cpu(findData.Gid);
inode->i_nlink = le64_to_cpu(findData.Nlinks);
spin_lock(&inode->i_lock);
if (is_size_safe_to_change(cifsInfo, end_of_file)) {
/* can not safely change the file size here if the
client is writing to it due to potential races */
i_size_write(inode, end_of_file);
/* blksize needs to be multiple of two. So safer to default to
@@ -162,6 +162,7 @@ int cifs_get_inode_info_unix(struct inode **pinode,
/* for this calculation */
inode->i_blocks = (512 - 1 + num_of_bytes) >> 9;
}
spin_unlock(&inode->i_lock);
if (num_of_bytes < end_of_file)
cFYI(1, ("allocation size less than end of file"));
@@ -496,6 +497,8 @@ int cifs_get_inode_info(struct inode **pinode,
/* BB add code here -
validate if device or weird share or device type? */
}
spin_lock(&inode->i_lock);
if (is_size_safe_to_change(cifsInfo, le64_to_cpu(pfindData->EndOfFile))) {
/* can not safely shrink the file size here if the
client is writing to it due to potential races */
@@ -506,6 +509,7 @@ int cifs_get_inode_info(struct inode **pinode,
inode->i_blocks = (512 - 1 + le64_to_cpu(
pfindData->AllocationSize)) >> 9;
}
spin_unlock(&inode->i_lock);
inode->i_nlink = le32_to_cpu(pfindData->NumberOfLinks);
@@ -834,8 +838,10 @@ int cifs_rmdir(struct inode *inode, struct dentry *direntry)
if (!rc) {
drop_nlink(inode);
spin_lock(&direntry->d_inode->i_lock);
i_size_write(direntry->d_inode,0);
clear_nlink(direntry->d_inode);
spin_unlock(&direntry->d_inode->i_lock);
}
cifsInode = CIFS_I(direntry->d_inode);
@@ -1128,6 +1134,46 @@ static int cifs_truncate_page(struct address_space *mapping, loff_t from)
return rc;
}
int cifs_vmtruncate(struct inode * inode, loff_t offset)
{
struct address_space *mapping = inode->i_mapping;
unsigned long limit;
if (inode->i_size < offset)
goto do_expand;
/*
* truncation of in-use swapfiles is disallowed - it would cause
* subsequent swapout to scribble on the now-freed blocks.
*/
if (IS_SWAPFILE(inode))
goto out_busy;
spin_lock(&inode->i_lock);
i_size_write(inode, offset);
spin_unlock(&inode->i_lock);
unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
truncate_inode_pages(mapping, offset);
goto out_truncate;
do_expand:
limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
if (limit != RLIM_INFINITY && offset > limit)
goto out_sig;
if (offset > inode->i_sb->s_maxbytes)
goto out_big;
i_size_write(inode, offset);
out_truncate:
if (inode->i_op && inode->i_op->truncate)
inode->i_op->truncate(inode);
return 0;
out_sig:
send_sig(SIGXFSZ, current, 0);
out_big:
return -EFBIG;
out_busy:
return -ETXTBSY;
}
int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
{
int xid;
@@ -1244,7 +1290,7 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
*/
if (rc == 0) {
rc = vmtruncate(direntry->d_inode, attrs->ia_size);
rc = cifs_vmtruncate(direntry->d_inode, attrs->ia_size);
cifs_truncate_page(direntry->d_inode->i_mapping,
direntry->d_inode->i_size);
} else