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[JFFS2] semaphore->mutex conversion

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Signed-off-by: David Woodhouse <dwmw2@infradead.org>
This commit is contained in:
David Woodhouse
2008-04-22 15:13:40 +01:00
parent 52f8301437
commit ced2207036
14 changed files with 168 additions and 167 deletions
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22
fs/jffs2/README.Locking
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@@ -14,7 +14,7 @@ be fairly close.
alloc_sem
---------
The alloc_sem is a per-filesystem semaphore, used primarily to ensure
The alloc_sem is a per-filesystem mutex, used primarily to ensure
contiguous allocation of space on the medium. It is automatically
obtained during space allocations (jffs2_reserve_space()) and freed
upon write completion (jffs2_complete_reservation()). Note that
@@ -41,10 +41,10 @@ if the wbuf is currently holding any data is permitted, though.
Ordering constraints: See f->sem.
File Semaphore f->sem
File Mutex f->sem
---------------------
This is the JFFS2-internal equivalent of the inode semaphore i->i_sem.
This is the JFFS2-internal equivalent of the inode mutex i->i_sem.
It protects the contents of the jffs2_inode_info private inode data,
including the linked list of node fragments (but see the notes below on
erase_completion_lock), etc.
@@ -60,14 +60,14 @@ lead to deadlock, unless we played games with unlocking the i_sem
before calling the space allocation functions.
Instead of playing such games, we just have an extra internal
semaphore, which is obtained by the garbage collection code and also
mutex, which is obtained by the garbage collection code and also
by the normal file system code _after_ allocation of space.
Ordering constraints:
1. Never attempt to allocate space or lock alloc_sem with
any f->sem held.
2. Never attempt to lock two file semaphores in one thread.
2. Never attempt to lock two file mutexes in one thread.
No ordering rules have been made for doing so.
@@ -86,8 +86,8 @@ a simple spin_lock() rather than spin_lock_bh().
Note that the per-inode list of physical nodes (f->nodes) is a special
case. Any changes to _valid_ nodes (i.e. ->flash_offset & 1 == 0) in
the list are protected by the file semaphore f->sem. But the erase
code may remove _obsolete_ nodes from the list while holding only the
the list are protected by the file mutex f->sem. But the erase code
may remove _obsolete_ nodes from the list while holding only the
erase_completion_lock. So you can walk the list only while holding the
erase_completion_lock, and can drop the lock temporarily mid-walk as
long as the pointer you're holding is to a _valid_ node, not an
@@ -124,10 +124,10 @@ Ordering constraints:
erase_free_sem
--------------
This semaphore is only used by the erase code which frees obsolete
node references and the jffs2_garbage_collect_deletion_dirent()
function. The latter function on NAND flash must read _obsolete_ nodes
to determine whether the 'deletion dirent' under consideration can be
This mutex is only used by the erase code which frees obsolete node
references and the jffs2_garbage_collect_deletion_dirent() function.
The latter function on NAND flash must read _obsolete_ nodes to
determine whether the 'deletion dirent' under consideration can be
discarded or whether it is still required to show that an inode has
been unlinked. Because reading from the flash may sleep, the
erase_completion_lock cannot be held, so an alternative, more