[PATCH 26/37] xfs: kill XBF_DONTBLOCK

Dave Chinner
2012-04-23T05:59:54Z

From: Dave Chinner <dchinner@redhat.com>

Just about all callers of xfs_buf_read() and xfs_buf_get() use XBF_DONTBLOCK.
This is used to make memory allocation use GFP_NOFS rather than GFP_KERNEL to
avoid recursion through memory reclaim back into the filesystem.

All the blocking get calls in growfs occur inside a transaction, even though
they are no part of the transaction, so all allocation will be GFP_NOFS due to
the task flag PF_TRANS being set. The blocking read calls occur during log
recovery, so they will probably be unaffected by converting to GFP_NOFS
allocations.

Hence make XBF_DONTBLOCK behaviour always occur for buffers and kill the flag.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
---
fs/xfs/xfs_attr.c | 3 +--
fs/xfs/xfs_buf.c | 18 +++++++-----------
fs/xfs/xfs_buf.h | 2 --
fs/xfs/xfs_trans_buf.c | 25 ++++---------------------
fs/xfs/xfs_vnodeops.c | 4 ++--
5 files changed, 14 insertions(+), 38 deletions(-)

diff --git a/fs/xfs/xfs_attr.c b/fs/xfs/xfs_attr.c
index ad85bed..0960bb6 100644
--- a/fs/xfs/xfs_attr.c
+++ b/fs/xfs/xfs_attr.c
@@ -2114,8 +2114,7 @@ xfs_attr_rmtval_set(xfs_da_args_t *args)
dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
blkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);

- bp = xfs_buf_get(mp->m_ddev_targp, dblkno, blkcnt,
- XBF_DONT_BLOCK);
+ bp = xfs_buf_get(mp->m_ddev_targp, dblkno, blkcnt, 0);
if (!bp)
return ENOMEM;

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 8366348..59e3916 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -56,11 +56,7 @@ static struct workqueue_struct *xfslogd_workqueue;
#endif

#define xb_to_gfp(flags) \
- ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : \
- ((flags) & XBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)
-
-#define xb_to_km(flags) \
- (((flags) & XBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)
+ ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)

static inline int
@@ -178,14 +174,14 @@ xfs_buf_alloc(
{
struct xfs_buf *bp;

- bp = kmem_zone_zalloc(xfs_buf_zone, xb_to_km(flags));
+ bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
if (unlikely(!bp))
return NULL;

/*
* We don't want certain flags to appear in b_flags.
*/
- flags &= ~(XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);
+ flags &= ~(XBF_MAPPED|XBF_READ_AHEAD);

atomic_set(&bp->b_hold, 1);
atomic_set(&bp->b_lru_ref, 1);
@@ -239,7 +235,7 @@ _xfs_buf_get_pages(
bp->b_pages = bp->b_page_array;
} else {
bp->b_pages = kmem_alloc(sizeof(struct page *) *
- page_count, xb_to_km(flags));
+ page_count, KM_NOFS);
if (bp->b_pages == NULL)
return -ENOMEM;
}
@@ -316,7 +312,7 @@ xfs_buf_allocate_memory(
*/
size = BBTOB(bp->b_length);
if (size < PAGE_SIZE) {
- bp->b_addr = kmem_alloc(size, xb_to_km(flags));
+ bp->b_addr = kmem_alloc(size, KM_NOFS);
if (!bp->b_addr) {
/* low memory - use alloc_page loop instead */
goto use_alloc_page;
@@ -659,7 +655,7 @@ xfs_buf_readahead(
return;

xfs_buf_read(target, blkno, numblks,
- XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD|XBF_DONT_BLOCK);
+ XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD);
}

/*
@@ -750,7 +746,7 @@ xfs_buf_associate_memory(
bp->b_pages = NULL;
bp->b_addr = mem;

- rval = _xfs_buf_get_pages(bp, page_count, XBF_DONT_BLOCK);
+ rval = _xfs_buf_get_pages(bp, page_count, 0);
if (rval)
return rval;

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 512d9a6..846dee3 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -53,7 +53,6 @@ typedef enum {

/* flags used only as arguments to access routines */
#define XBF_TRYLOCK (1 << 16)/* lock requested, but do not wait */
-#define XBF_DONT_BLOCK (1 << 17)/* do not block in current thread */

/* flags used only internally */
#define _XBF_PAGES (1 << 20)/* backed by refcounted pages */
@@ -74,7 +73,6 @@ typedef unsigned int xfs_buf_flags_t;
{ XBF_FUA, "FUA" }, \
{ XBF_FLUSH, "FLUSH" }, \
{ XBF_TRYLOCK, "TRYLOCK" }, /* should never be set */\
- { XBF_DONT_BLOCK, "DONT_BLOCK" }, /* ditto */\
{ _XBF_PAGES, "PAGES" }, \
{ _XBF_KMEM, "KMEM" }, \
{ _XBF_DELWRI_Q, "DELWRI_Q" }
diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index 5e4cf61..ccc6da1 100644
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -148,8 +148,7 @@ xfs_trans_get_buf(xfs_trans_t *tp,
* Default to a normal get_buf() call if the tp is NULL.
*/
if (tp == NULL)
- return xfs_buf_get(target_dev, blkno, len,
- flags | XBF_DONT_BLOCK);
+ return xfs_buf_get(target_dev, blkno, len, flags);

/*
* If we find the buffer in the cache with this transaction
@@ -174,15 +173,7 @@ xfs_trans_get_buf(xfs_trans_t *tp,
return (bp);
}

- /*
- * We always specify the XBF_DONT_BLOCK flag within a transaction
- * so that get_buf does not try to push out a delayed write buffer
- * which might cause another transaction to take place (if the
- * buffer was delayed alloc). Such recursive transactions can
- * easily deadlock with our current transaction as well as cause
- * us to run out of stack space.
- */
- bp = xfs_buf_get(target_dev, blkno, len, flags | XBF_DONT_BLOCK);
+ bp = xfs_buf_get(target_dev, blkno, len, flags);
if (bp == NULL) {
return NULL;
}
@@ -283,7 +274,7 @@ xfs_trans_read_buf(
* Default to a normal get_buf() call if the tp is NULL.
*/
if (tp == NULL) {
- bp = xfs_buf_read(target, blkno, len, flags | XBF_DONT_BLOCK);
+ bp = xfs_buf_read(target, blkno, len, flags);
if (!bp)
return (flags & XBF_TRYLOCK) ?
EAGAIN : XFS_ERROR(ENOMEM);
@@ -367,15 +358,7 @@ xfs_trans_read_buf(
return 0;
}

- /*
- * We always specify the XBF_DONT_BLOCK flag within a transaction
- * so that get_buf does not try to push out a delayed write buffer
- * which might cause another transaction to take place (if the
- * buffer was delayed alloc). Such recursive transactions can
- * easily deadlock with our current transaction as well as cause
- * us to run out of stack space.
- */
- bp = xfs_buf_read(target, blkno, len, flags | XBF_DONT_BLOCK);
+ bp = xfs_buf_read(target, blkno, len, flags);
if (bp == NULL) {
*bpp = NULL;
return (flags & XBF_TRYLOCK) ?
diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 8f99c77..6c18745 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -82,7 +82,7 @@ xfs_readlink_bmap(
byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);

bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt),
- XBF_MAPPED | XBF_DONT_BLOCK);
+ XBF_MAPPED);
if (!bp)
return XFS_ERROR(ENOMEM);
error = bp->b_error;
@@ -1966,7 +1966,7 @@ xfs_zero_remaining_bytes(

bp = xfs_buf_get_uncached(XFS_IS_REALTIME_INODE(ip) ?
mp->m_rtdev_targp : mp->m_ddev_targp,
- BTOBB(mp->m_sb.sb_blocksize), XBF_DONT_BLOCK);
+ BTOBB(mp->m_sb.sb_blocksize), 0);
if (!bp)
return XFS_ERROR(ENOMEM);

--
1.7.9.5