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afs: Fix unlink 

Repeating creation and deletion of a file on an afs mount will run the box
out of memory, e.g.:

	dd if=/dev/zero of=/afs/scratch/m0 bs=$((1024*1024)) count=512
	rm /afs/scratch/m0

The problem seems to be that it's not properly decrementing the nlink count
so that the inode can be scrapped.

Note that this doesn't fix local creation followed by remote deletion.
That's harder to handle and will require a separate patch as we're not told
that the file has been deleted - only that the directory has changed.

Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2018-01-02 10:02:19 +00:00
parent 7888da9583
commit 440fbc3a8a
2 changed files with 33 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
fs/afs/dir.c
View File

@ -895,20 +895,38 @@ error:
* However, if we didn't have a callback promise outstanding, or it was * However, if we didn't have a callback promise outstanding, or it was
* outstanding on a different server, then it won't break it either... * outstanding on a different server, then it won't break it either...
*/ */
static int afs_dir_remove_link(struct dentry *dentry, struct key *key) static int afs_dir_remove_link(struct dentry *dentry, struct key *key,
unsigned long d_version_before,
unsigned long d_version_after)
{ {
bool dir_valid;
int ret = 0; int ret = 0;
/* There were no intervening changes on the server if the version
* number we got back was incremented by exactly 1.
*/
dir_valid = (d_version_after == d_version_before + 1);
if (d_really_is_positive(dentry)) { if (d_really_is_positive(dentry)) {
struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry)); struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) if (dir_valid) {
kdebug("AFS_VNODE_DELETED"); drop_nlink(&vnode->vfs_inode);
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags); if (vnode->vfs_inode.i_nlink == 0) {
set_bit(AFS_VNODE_DELETED, &vnode->flags);
ret = afs_validate(vnode, key); clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
if (ret == -ESTALE) }
ret = 0; ret = 0;
} else {
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
kdebug("AFS_VNODE_DELETED");
ret = afs_validate(vnode, key);
if (ret == -ESTALE)
ret = 0;
}
_debug("nlink %d [val %d]", vnode->vfs_inode.i_nlink, ret); _debug("nlink %d [val %d]", vnode->vfs_inode.i_nlink, ret);
} }
@ -923,6 +941,7 @@ static int afs_unlink(struct inode *dir, struct dentry *dentry)
struct afs_fs_cursor fc; struct afs_fs_cursor fc;
struct afs_vnode *dvnode = AFS_FS_I(dir), *vnode; struct afs_vnode *dvnode = AFS_FS_I(dir), *vnode;
struct key *key; struct key *key;
unsigned long d_version = (unsigned long)dentry->d_fsdata;
int ret; int ret;
_enter("{%x:%u},{%pd}", _enter("{%x:%u},{%pd}",
@ -955,7 +974,9 @@ static int afs_unlink(struct inode *dir, struct dentry *dentry)
afs_vnode_commit_status(&fc, dvnode, fc.cb_break); afs_vnode_commit_status(&fc, dvnode, fc.cb_break);
ret = afs_end_vnode_operation(&fc); ret = afs_end_vnode_operation(&fc);
if (ret == 0) if (ret == 0)
ret = afs_dir_remove_link(dentry, key); ret = afs_dir_remove_link(
dentry, key, d_version,
(unsigned long)dvnode->status.data_version);
} }
error_key: error_key:

4
fs/afs/inode.c
View File

@ -377,6 +377,10 @@ int afs_validate(struct afs_vnode *vnode, struct key *key)
} }
read_sequnlock_excl(&vnode->cb_lock); read_sequnlock_excl(&vnode->cb_lock);
if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
clear_nlink(&vnode->vfs_inode);
if (valid) if (valid)
goto valid; goto valid;