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authorSean Anderson <seanga2@gmail.com>2018-05-24 05:29:10 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2018-05-26 10:38:09 +0300
commit965de0ec351a580874dcc4c1eaeae78dd9d1c369 (patch)
treef1ff1e2ee153d9be7ac64553b375bd6de63c5aab /Documentation/filesystems/Locking
parent030c7e0bb723e3de6354d1a85df0543197efec1a (diff)
downloadlinux-965de0ec351a580874dcc4c1eaeae78dd9d1c369.tar.xz
Documentation: filesystems: update filesystem locking documentation
Documentation/filesystems/Locking no longer reflects current locking semantics. i_mutex is no longer used for locking, and has been superseded by i_rwsem. Additionally, ->iterate_shared() was not documented. Signed-off-by: Sean Anderson <seanga2@gmail.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/filesystems/Locking')
-rw-r--r--Documentation/filesystems/Locking43
1 files changed, 24 insertions, 19 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 75d2d57e2c44..15853d522941 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -69,31 +69,31 @@ prototypes:
locking rules:
all may block
- i_mutex(inode)
-lookup: yes
-create: yes
-link: yes (both)
-mknod: yes
-symlink: yes
-mkdir: yes
-unlink: yes (both)
-rmdir: yes (both) (see below)
-rename: yes (all) (see below)
+ i_rwsem(inode)
+lookup: shared
+create: exclusive
+link: exclusive (both)
+mknod: exclusive
+symlink: exclusive
+mkdir: exclusive
+unlink: exclusive (both)
+rmdir: exclusive (both)(see below)
+rename: exclusive (all) (see below)
readlink: no
get_link: no
-setattr: yes
+setattr: exclusive
permission: no (may not block if called in rcu-walk mode)
get_acl: no
getattr: no
listxattr: no
fiemap: no
update_time: no
-atomic_open: yes
+atomic_open: exclusive
tmpfile: no
- Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
-victim.
+ Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem
+ exclusive on victim.
cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
See Documentation/filesystems/directory-locking for more detailed discussion
@@ -111,10 +111,10 @@ prototypes:
locking rules:
all may block
- i_mutex(inode)
+ i_rwsem(inode)
list: no
get: no
-set: yes
+set: exclusive
--------------------------- super_operations ---------------------------
prototypes:
@@ -217,14 +217,14 @@ prototypes:
locking rules:
All except set_page_dirty and freepage may block
- PageLocked(page) i_mutex
+ PageLocked(page) i_rwsem
writepage: yes, unlocks (see below)
readpage: yes, unlocks
writepages:
set_page_dirty no
readpages:
-write_begin: locks the page yes
-write_end: yes, unlocks yes
+write_begin: locks the page exclusive
+write_end: yes, unlocks exclusive
bmap:
invalidatepage: yes
releasepage: yes
@@ -439,6 +439,7 @@ prototypes:
ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iterate) (struct file *, struct dir_context *);
+ int (*iterate_shared) (struct file *, struct dir_context *);
unsigned int (*poll) (struct file *, struct poll_table_struct *);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
@@ -480,6 +481,10 @@ mutex or just to use i_size_read() instead.
Note: this does not protect the file->f_pos against concurrent modifications
since this is something the userspace has to take care about.
+->iterate() is called with i_rwsem exclusive.
+
+->iterate_shared() is called with i_rwsem at least shared.
+
->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags.
Most instances call fasync_helper(), which does that maintenance, so it's
not normally something one needs to worry about. Return values > 0 will be