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doc: document scope NOFS, NOIO APIs

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Although the api is documented in the source code Ted has pointed out
that there is no mention in the core-api Documentation and there are
people looking there to find answers how to use a specific API.

Requested-by: "Theodore Y. Ts'o" <tytso@mit.edu>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Michal Hocko
2018-05-29 10:26:44 +02:00
committed by Jonathan Corbet
parent 8962e40c19
commit 46ca359955
3 changed files with 100 additions and 0 deletions
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38
include/linux/sched/mm.h
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@@ -170,6 +170,17 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
static inline void fs_reclaim_release(gfp_t gfp_mask) { }
#endif
/**
* memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
*
* This functions marks the beginning of the GFP_NOIO allocation scope.
* All further allocations will implicitly drop __GFP_IO flag and so
* they are safe for the IO critical section from the allocation recursion
* point of view. Use memalloc_noio_restore to end the scope with flags
* returned by this function.
*
* This function is safe to be used from any context.
*/
static inline unsigned int memalloc_noio_save(void)
{
unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
@@ -177,11 +188,30 @@ static inline unsigned int memalloc_noio_save(void)
return flags;
}
/**
* memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
* @flags: Flags to restore.
*
* Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
* Always make sure that that the given flags is the return value from the
* pairing memalloc_noio_save call.
*/
static inline void memalloc_noio_restore(unsigned int flags)
{
current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
}
/**
* memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
*
* This functions marks the beginning of the GFP_NOFS allocation scope.
* All further allocations will implicitly drop __GFP_FS flag and so
* they are safe for the FS critical section from the allocation recursion
* point of view. Use memalloc_nofs_restore to end the scope with flags
* returned by this function.
*
* This function is safe to be used from any context.
*/
static inline unsigned int memalloc_nofs_save(void)
{
unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
@@ -189,6 +219,14 @@ static inline unsigned int memalloc_nofs_save(void)
return flags;
}
/**
* memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
* @flags: Flags to restore.
*
* Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
* Always make sure that that the given flags is the return value from the
* pairing memalloc_nofs_save call.
*/
static inline void memalloc_nofs_restore(unsigned int flags)
{
current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;