From: Jan Kara <jack@suse.cz>
Attached patch updates documentation in Documentation/filesystems/Locking
to match the current state of quota code. Also a few comments in quota
code are updated.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/Documentation/filesystems/Locking | 62 ++++++++++++++++++++++--------
25-akpm/fs/dquot.c | 5 +-
2 files changed, 50 insertions(+), 17 deletions(-)
diff -puN Documentation/filesystems/Locking~update-documentation-filesystems-locking Documentation/filesystems/Locking
--- 25/Documentation/filesystems/Locking~update-documentation-filesystems-locking Wed Feb 9 14:33:41 2005
+++ 25-akpm/Documentation/filesystems/Locking Wed Feb 9 14:33:41 2005
@@ -104,6 +104,8 @@ prototypes:
void (*clear_inode) (struct inode *);
void (*umount_begin) (struct super_block *);
int (*show_options)(struct seq_file *, struct vfsmount *);
+ ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
+ ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
locking rules:
All may block.
@@ -126,10 +128,17 @@ remount_fs: no yes maybe (see below)
clear_inode: no
umount_begin: yes no no
show_options: no (vfsmount->sem)
+quota_read: no no no (see below)
+quota_write: no no no (see below)
->read_inode() is not a method - it's a callback used in iget().
->remount_fs() will have the s_umount lock if it's already mounted.
When called from get_sb_single, it does NOT have the s_umount lock.
+->quota_read() and ->quota_write() functions are both guaranteed to
+be the only ones operating on the quota file by the quota code (via
+dqio_sem) (unless an admin really wants to screw up something and
+writes to quota files with quotas on). For other details about locking
+see also dquot_operations section.
--------------------------- file_system_type ---------------------------
prototypes:
@@ -442,23 +451,46 @@ in sys_read() and friends.
--------------------------- dquot_operations -------------------------------
prototypes:
- void (*initialize) (struct inode *, short);
- void (*drop) (struct inode *);
- int (*alloc_block) (const struct inode *, unsigned long, char);
+ int (*initialize) (struct inode *, int);
+ int (*drop) (struct inode *);
+ int (*alloc_space) (struct inode *, qsize_t, int);
int (*alloc_inode) (const struct inode *, unsigned long);
- void (*free_block) (const struct inode *, unsigned long);
- void (*free_inode) (const struct inode *, unsigned long);
- int (*transfer) (struct dentry *, struct iattr *);
+ int (*free_space) (struct inode *, qsize_t);
+ int (*free_inode) (const struct inode *, unsigned long);
+ int (*transfer) (struct inode *, struct iattr *);
+ int (*write_dquot) (struct dquot *);
+ int (*acquire_dquot) (struct dquot *);
+ int (*release_dquot) (struct dquot *);
+ int (*mark_dirty) (struct dquot *);
+ int (*write_info) (struct super_block *, int);
+
+These operations are intended to be more or less wrapping functions that ensure
+a proper locking wrt the filesystem and call the generic quota operations.
+
+What filesystem should expect from the generic quota functions:
+
+ FS recursion Held locks when called
+initialize: yes maybe dqonoff_sem
+drop: yes -
+alloc_space: ->mark_dirty() -
+alloc_inode: ->mark_dirty() -
+free_space: ->mark_dirty() -
+free_inode: ->mark_dirty() -
+transfer: yes -
+write_dquot: yes dqonoff_sem or dqptr_sem
+acquire_dquot: yes dqonoff_sem or dqptr_sem
+release_dquot: yes dqonoff_sem or dqptr_sem
+mark_dirty: no -
+write_info: yes dqonoff_sem
+
+FS recursion means calling ->quota_read() and ->quota_write() from superblock
+operations.
+
+->alloc_space(), ->alloc_inode(), ->free_space(), ->free_inode() are called
+only directly by the filesystem and do not call any fs functions only
+the ->mark_dirty() operation.
-locking rules:
- BKL
-initialize: no
-drop: no
-alloc_block: yes
-alloc_inode: yes
-free_block: yes
-free_inode: yes
-transfer: no
+More details about quota locking can be found in fs/dquot.c.
--------------------------- vm_operations_struct -----------------------------
prototypes:
diff -puN fs/dquot.c~update-documentation-filesystems-locking fs/dquot.c
--- 25/fs/dquot.c~update-documentation-filesystems-locking Wed Feb 9 14:33:41 2005
+++ 25-akpm/fs/dquot.c Wed Feb 9 14:33:41 2005
@@ -1092,7 +1092,7 @@ warn_put_all:
}
/*
- * This is a non-blocking operation.
+ * This operation can block, but only after everything is updated
*/
int dquot_free_space(struct inode *inode, qsize_t number)
{
@@ -1128,7 +1128,7 @@ out_sub:
}
/*
- * This is a non-blocking operation.
+ * This operation can block, but only after everything is updated
*/
int dquot_free_inode(const struct inode *inode, unsigned long number)
{
@@ -1163,6 +1163,7 @@ int dquot_free_inode(const struct inode
* Transfer the number of inode and blocks from one diskquota to an other.
*
* This operation can block, but only after everything is updated
+ * A transaction must be started when entering this function.
*/
int dquot_transfer(struct inode *inode, struct iattr *iattr)
{
_