Introduce an EXT4_MB_FORCE_ALIGN flag that essentially enforces the same
behavior as EXT4_MB_HINT_ALIGNED however the alignment requirements are no
longer a hint but must be respected. If the allocator can't return aligned
blocks, then ENOSPC will be thrown.
This will be eventually used to guarantee aligned blocks to perform H/W
accelerated atomic writes.
Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
---
fs/ext4/ext4.h | 2 ++
fs/ext4/mballoc.c | 31 +++++++++++++++++++++++--------
include/trace/events/ext4.h | 1 +
3 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ab4f10f9031a..9b9d7a354736 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -224,6 +224,8 @@ enum criteria {
#define EXT4_MB_CR_BEST_AVAIL_LEN_OPTIMIZED 0x00020000
/* mballoc will try to align physical start to length (aka natural alignment) */
#define EXT4_MB_HINT_ALIGNED 0x40000
+/* Same as HINT_ALIGNED but fail allocation if alginment can't be guaranteed */
+#define EXT4_MB_FORCE_ALIGN 0x80000
struct ext4_allocation_request {
/* target inode for block we're allocating */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index db7c593873a9..412aa80bc6e7 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2872,12 +2872,21 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
ac->ac_criteria = cr;
if (ac->ac_criteria > CR_POWER2_ALIGNED &&
- ac->ac_flags & EXT4_MB_HINT_ALIGNED &&
ac->ac_g_ex.fe_len > 1) {
- ext4_warning_inode(
- ac->ac_inode,
- "Aligned allocation not possible, using unaligned allocation");
- ac->ac_flags &= ~EXT4_MB_HINT_ALIGNED;
+ if (ac->ac_flags & EXT4_MB_FORCE_ALIGN) {
+ ext4_warning_inode(
+ ac->ac_inode,
+ "Aligned allocation not possible, failing allocation");
+ ac->ac_status = AC_STATUS_BREAK;
+ goto exit;
+ }
+
+ if (ac->ac_flags & EXT4_MB_HINT_ALIGNED) {
+ ext4_warning_inode(
+ ac->ac_inode,
+ "Aligned allocation not possible, using unaligned allocation");
+ ac->ac_flags &= ~EXT4_MB_HINT_ALIGNED;
+ }
}
/*
@@ -3023,9 +3032,15 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
goto exit;
}
- WARN_ON_ONCE(!is_power_of_2(len));
- WARN_ON_ONCE(start % len);
- WARN_ON_ONCE(ac->ac_b_ex.fe_len < ac->ac_o_ex.fe_len);
+ if (WARN_ON_ONCE(!is_power_of_2(len)) ||
+ WARN_ON_ONCE(start % len) ||
+ WARN_ON_ONCE(ac->ac_b_ex.fe_len < ac->ac_o_ex.fe_len)) {
+ /* FORCE_ALIGN should error out if aligned blocks can't be found */
+ if (ac->ac_flags & EXT4_MB_FORCE_ALIGN) {
+ ac->ac_status = AC_STATUS_BREAK;
+ goto exit;
+ }
+ }
}
exit:
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index d9464ee764af..ebc1fb5ad57b 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -37,6 +37,7 @@ struct partial_cluster;
{ EXT4_MB_USE_ROOT_BLOCKS, "USE_ROOT_BLKS" }, \
{ EXT4_MB_USE_RESERVED, "USE_RESV" }, \
{ EXT4_MB_HINT_ALIGNED, "HINT_ALIGNED" }, \
+ { EXT4_MB_FORCE_ALIGN, "FORCE_ALIGN" }, \
{ EXT4_MB_STRICT_CHECK, "STRICT_CHECK" })
#define show_map_flags(flags) __print_flags(flags, "|", \
--
2.48.1
