[RFC] [PATCHv2 1/7] reiser4: block_alloc: add BA_SOME_SPACE flag for grabbing a fixed amount of space.

[Ivan Shapovalov <intelfx100@gmail.com>]

This is used for FITRIM ioctl which will iteratively grab, allocate and trim disk space
bit by bit to avoid starving the rest of system.

Signed-off-by: Ivan Shapovalov <intelfx100@gmail.com>
---
 fs/reiser4/block_alloc.c | 6 ++++++
 fs/reiser4/block_alloc.h | 5 ++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/reiser4/block_alloc.c b/fs/reiser4/block_alloc.c
index d3d730c..8797b43 100644
--- a/fs/reiser4/block_alloc.c
+++ b/fs/reiser4/block_alloc.c
@@ -276,6 +276,12 @@ reiser4_grab(reiser4_context * ctx, __u64 count, reiser4_ba_flags_t flags)
 
 	free_blocks = sbinfo->blocks_free;
 
+	if (flags & BA_SOME_SPACE) {
+		/* Reserve 25% of all free space. */
+		count = free_blocks;
+		do_div(count, 4);
+	}
+
 	if ((use_reserved && free_blocks < count) ||
 	    (!use_reserved && free_blocks < count + sbinfo->blocks_reserved)) {
 		ret = RETERR(-ENOSPC);
diff --git a/fs/reiser4/block_alloc.h b/fs/reiser4/block_alloc.h
index a4e98af..bfc6be9 100644
--- a/fs/reiser4/block_alloc.h
+++ b/fs/reiser4/block_alloc.h
@@ -79,7 +79,10 @@ enum reiser4_ba_flags {
 	BA_FORCE = (1 << 5),
 
 	/* use default start value for free blocks search. */
-	BA_USE_DEFAULT_SEARCH_START = (1 << 6)
+	BA_USE_DEFAULT_SEARCH_START = (1 << 6),
+
+	/* reserve some fixed amount of space */
+	BA_SOME_SPACE = (1 << 7),
 };
 
 typedef enum reiser4_ba_flags reiser4_ba_flags_t;
-- 
2.0.4