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update VFS documentation for method changes.

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2010-06-08 00:37:12 -04:00
parent b70a3e0702
commit 336fb3b97b
2 changed files with 39 additions and 10 deletions
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22
Documentation/filesystems/Locking
View file

@ -92,8 +92,8 @@ prototypes:
void (*destroy_inode)(struct inode *);
void (*dirty_inode) (struct inode *);
int (*write_inode) (struct inode *, int);
void (*drop_inode) (struct inode *);
void (*delete_inode) (struct inode *);
int (*drop_inode) (struct inode *);
void (*evict_inode) (struct inode *);
void (*put_super) (struct super_block *);
void (*write_super) (struct super_block *);
int (*sync_fs)(struct super_block *sb, int wait);
@ -101,14 +101,13 @@ prototypes:
int (*unfreeze_fs) (struct super_block *);
int (*statfs) (struct dentry *, struct kstatfs *);
int (*remount_fs) (struct super_block *, int *, char *);
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.
All may block [not true, see below]
None have BKL
s_umount
alloc_inode:
@ -116,22 +115,25 @@ destroy_inode:
dirty_inode: (must not sleep)
write_inode:
drop_inode: !!!inode_lock!!!
delete_inode:
evict_inode:
put_super: write
write_super: read
sync_fs: read
freeze_fs: read
unfreeze_fs: read
statfs: no
remount_fs: maybe (see below)
clear_inode:
statfs: maybe(read) (see below)
remount_fs: write
umount_begin: no
show_options: no (namespace_sem)
quota_read: no (see below)
quota_write: no (see below)
->remount_fs() will have the s_umount exclusive lock if it's already mounted.
When called from get_sb_single, it does NOT have the s_umount lock.
->statfs() has s_umount (shared) when called by ustat(2) (native or
compat), but that's an accident of bad API; s_umount is used to pin
the superblock down when we only have dev_t given us by userland to
identify the superblock. Everything else (statfs(), fstatfs(), etc.)
doesn't hold it when calling ->statfs() - superblock is pinned down
by resolving the pathname passed to syscall.
->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

27
Documentation/filesystems/porting
View file

@ -291,3 +291,30 @@ be in order of zeroing blocks using block_truncate_page or similar helpers,
size update and on finally on-disk truncation which should not fail.
inode_change_ok now includes the size checks for ATTR_SIZE and must be called
in the beginning of ->setattr unconditionally.
[mandatory]
->clear_inode() and ->delete_inode() are gone; ->evict_inode() should
be used instead. It gets called whenever the inode is evicted, whether it has
remaining links or not. Caller does *not* evict the pagecache or inode-associated
metadata buffers; getting rid of those is responsibility of method, as it had
been for ->delete_inode().
->drop_inode() returns int now; it's called on final iput() with inode_lock
held and it returns true if filesystems wants the inode to be dropped. As before,
generic_drop_inode() is still the default and it's been updated appropriately.
generic_delete_inode() is also alive and it consists simply of return 1. Note that
all actual eviction work is done by caller after ->drop_inode() returns.
clear_inode() is gone; use end_writeback() instead. As before, it must
be called exactly once on each call of ->evict_inode() (as it used to be for
each call of ->delete_inode()). Unlike before, if you are using inode-associated
metadata buffers (i.e. mark_buffer_dirty_inode()), it's your responsibility to
call invalidate_inode_buffers() before end_writeback().
No async writeback (and thus no calls of ->write_inode()) will happen
after end_writeback() returns, so actions that should not overlap with ->write_inode()
(e.g. freeing on-disk inode if i_nlink is 0) ought to be done after that call.
NOTE: checking i_nlink in the beginning of ->write_inode() and bailing out
if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput()
may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly
free the on-disk inode, you may end up doing that while ->write_inode() is writing
to it.