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authorMichal Hocko <mhocko@suse.com>2018-05-29 10:26:44 +0200
committerJonathan Corbet <corbet@lwn.net>2018-05-29 14:45:42 +0200
commit46ca359955fee63486dc1cfc528ae5692bb16dcd (patch)
tree5b50eea6676820b268168e0dd9ab4c7b9a2c5b1a /include
parentdocs: update kernel versions and dates in tables (diff)
downloadlinux-46ca359955fee63486dc1cfc528ae5692bb16dcd.tar.xz
linux-46ca359955fee63486dc1cfc528ae5692bb16dcd.zip
doc: document scope NOFS, NOIO APIs
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/sched/mm.h38
1 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 4e1411bbbcfc..76a8cb4ef178 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -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;