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Date: Fri, 16 Jun 2017 18:15:29 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: akpm@...ux-foundation.org
Cc: Jan Kara <jack@...e.cz>, linux-nvdimm@...ts.01.org,
linux-api@...r.kernel.org, Dave Chinner <david@...morbit.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Jeff Moyer <jmoyer@...hat.com>, linux-fsdevel@...r.kernel.org,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
Christoph Hellwig <hch@....de>
Subject: [RFC PATCH 1/2] mm: introduce bmap_walk()
Refactor the core of generic_swapfile_activate() into bmap_walk() so
that it can be used by a new daxfile_activate() helper (to be added).
There should be no functional differences as a result of this change,
although it does add the capability to perform the bmap with a given
page-size. This is in support of daxfile users that want to ensure huge
page usage.
Cc: Jan Kara <jack@...e.cz>
Cc: Jeff Moyer <jmoyer@...hat.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Dave Chinner <david@...morbit.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
mm/page_io.c | 86 +++++++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 67 insertions(+), 19 deletions(-)
diff --git a/mm/page_io.c b/mm/page_io.c
index 23f6d0d3470f..5cec9a3d49f2 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -135,11 +135,22 @@ static void end_swap_bio_read(struct bio *bio)
bio_put(bio);
}
-int generic_swapfile_activate(struct swap_info_struct *sis,
- struct file *swap_file,
- sector_t *span)
+enum bmap_check {
+ BMAP_WALK_UNALIGNED,
+ BMAP_WALK_DISCONTIG,
+ BMAP_WALK_FULLPAGE,
+ BMAP_WALK_DONE,
+};
+
+typedef int (*bmap_check_fn)(sector_t block, unsigned long page_no,
+ enum bmap_check type, void *ctx);
+
+static int bmap_walk(struct file *file, const unsigned page_size,
+ const unsigned long page_max, sector_t *span,
+ bmap_check_fn check, void *ctx)
{
- struct address_space *mapping = swap_file->f_mapping;
+ struct address_space *mapping = file->f_mapping;
+ const unsigned page_shift = ilog2(page_size);
struct inode *inode = mapping->host;
unsigned blocks_per_page;
unsigned long page_no;
@@ -152,7 +163,7 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
int ret;
blkbits = inode->i_blkbits;
- blocks_per_page = PAGE_SIZE >> blkbits;
+ blocks_per_page = page_size >> blkbits;
/*
* Map all the blocks into the extent list. This code doesn't try
@@ -162,7 +173,7 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
page_no = 0;
last_block = i_size_read(inode) >> blkbits;
while ((probe_block + blocks_per_page) <= last_block &&
- page_no < sis->max) {
+ page_no < page_max) {
unsigned block_in_page;
sector_t first_block;
@@ -173,11 +184,15 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
goto bad_bmap;
/*
- * It must be PAGE_SIZE aligned on-disk
+ * It must be @page_size aligned on-disk
*/
if (first_block & (blocks_per_page - 1)) {
probe_block++;
- goto reprobe;
+ ret = check(first_block, page_no,
+ BMAP_WALK_UNALIGNED, ctx);
+ if (ret == -EAGAIN)
+ goto reprobe;
+ goto bad_bmap;
}
for (block_in_page = 1; block_in_page < blocks_per_page;
@@ -190,11 +205,15 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
if (block != first_block + block_in_page) {
/* Discontiguity */
probe_block++;
- goto reprobe;
+ ret = check(first_block, page_no,
+ BMAP_WALK_DISCONTIG, ctx);
+ if (ret == -EAGAIN)
+ goto reprobe;
+ goto bad_bmap;
}
}
- first_block >>= (PAGE_SHIFT - blkbits);
+ first_block >>= (page_shift - blkbits);
if (page_no) { /* exclude the header page */
if (first_block < lowest_block)
lowest_block = first_block;
@@ -203,9 +222,9 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
}
/*
- * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
+ * We found a @page_size-{length,aligned} run of blocks
*/
- ret = add_swap_extent(sis, page_no, 1, first_block);
+ ret = check(first_block, page_no, BMAP_WALK_FULLPAGE, ctx);
if (ret < 0)
goto out;
nr_extents += ret;
@@ -215,20 +234,49 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
continue;
}
ret = nr_extents;
- *span = 1 + highest_block - lowest_block;
- if (page_no == 0)
- page_no = 1; /* force Empty message */
- sis->max = page_no;
- sis->pages = page_no - 1;
- sis->highest_bit = page_no - 1;
+ if (span)
+ *span = 1 + highest_block - lowest_block;
+ check(highest_block, page_no, BMAP_WALK_DONE, ctx);
out:
return ret;
bad_bmap:
- pr_err("swapon: swapfile has holes\n");
ret = -EINVAL;
goto out;
}
+static int swapfile_check(sector_t block, unsigned long page_no,
+ enum bmap_check type, void *_sis)
+{
+ struct swap_info_struct *sis = _sis;
+
+ if (type == BMAP_WALK_DONE) {
+ if (page_no == 0)
+ page_no = 1; /* force Empty message */
+ sis->max = page_no;
+ sis->pages = page_no - 1;
+ sis->highest_bit = page_no - 1;
+ return 0;
+ }
+
+ if (type != BMAP_WALK_FULLPAGE)
+ return -EAGAIN;
+
+ return add_swap_extent(sis, page_no, 1, block);
+}
+
+int generic_swapfile_activate(struct swap_info_struct *sis,
+ struct file *swap_file,
+ sector_t *span)
+{
+ int rc = bmap_walk(swap_file, PAGE_SIZE, sis->max, span,
+ swapfile_check, sis);
+
+ if (rc < 0)
+ pr_err("swapon: swapfile has holes\n");
+
+ return rc;
+}
+
/*
* We may have stale swap cache pages in memory: notice
* them here and get rid of the unnecessary final write.
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