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Message-ID: <20260112034330.2263034-1-hsiangkao@linux.alibaba.com>
Date: Mon, 12 Jan 2026 11:43:30 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>,
Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: [PATCH] erofs: tidy up synchronous decompression
- Get rid of `sbi->opt.max_sync_decompress_pages` since it's fixed as
3 all the time;
- Add Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES in bytes instead of in pages,
since for non-4K pages, 3-page limitation makes no sense;
- Move `sync_decompress` to sbi to avoid unexpected remount impact;
- Fold z_erofs_is_sync_decompress() into its caller;
- Better description of sysfs entry `sync_decompress`.
Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
---
Documentation/ABI/testing/sysfs-fs-erofs | 14 ++++++----
fs/erofs/internal.h | 5 +---
fs/erofs/super.c | 3 +-
fs/erofs/sysfs.c | 2 +-
fs/erofs/zdata.c | 35 +++++++++---------------
5 files changed, 25 insertions(+), 34 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
index 76d9808ed581..b9243c7f28d7 100644
--- a/Documentation/ABI/testing/sysfs-fs-erofs
+++ b/Documentation/ABI/testing/sysfs-fs-erofs
@@ -10,12 +10,16 @@ Description: Shows all enabled kernel features.
What: /sys/fs/erofs/<disk>/sync_decompress
Date: November 2021
Contact: "Huang Jianan" <huangjianan@...o.com>
-Description: Control strategy of sync decompression:
+Description: Control strategy of synchronous decompression. Synchronous
+ decompression tries to decompress in the reader thread for
+ synchronous reads and small asynchronous reads (<= 12 KiB):
- - 0 (default, auto): enable for readpage, and enable for
- readahead on atomic contexts only.
- - 1 (force on): enable for readpage and readahead.
- - 2 (force off): disable for all situations.
+ - 0 (auto, default): apply to synchronous reads only, but will
+ switch to 1 (force on) if any decompression
+ request is detected in atomic contexts;
+ - 1 (force on): apply to synchronous reads and small
+ asynchronous reads;
+ - 2 (force off): disable synchronous decompression completely.
What: /sys/fs/erofs/<disk>/drop_caches
Date: November 2024
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index f7f622836198..87edbb4366d1 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -59,10 +59,6 @@ enum {
struct erofs_mount_opts {
/* current strategy of how to use managed cache */
unsigned char cache_strategy;
- /* strategy of sync decompression (0 - auto, 1 - force on, 2 - force off) */
- unsigned int sync_decompress;
- /* threshold for decompression synchronously */
- unsigned int max_sync_decompress_pages;
unsigned int mount_opt;
};
@@ -116,6 +112,7 @@ struct erofs_sb_info {
/* managed XArray arranged in physical block number */
struct xarray managed_pslots;
+ unsigned int sync_decompress; /* strategy for sync decompression */
unsigned int shrinker_run_no;
u16 available_compr_algs;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 937a215f626c..9f90d410ab94 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -372,8 +372,7 @@ static void erofs_default_options(struct erofs_sb_info *sbi)
{
#ifdef CONFIG_EROFS_FS_ZIP
sbi->opt.cache_strategy = EROFS_ZIP_CACHE_READAROUND;
- sbi->opt.max_sync_decompress_pages = 3;
- sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_AUTO;
+ sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_AUTO;
#endif
#ifdef CONFIG_EROFS_FS_XATTR
set_opt(&sbi->opt, XATTR_USER);
diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index 1e0658a1d95b..86b22b9f0c19 100644
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -59,7 +59,7 @@ static struct erofs_attr erofs_attr_##_name = { \
#define ATTR_LIST(name) (&erofs_attr_##name.attr)
#ifdef CONFIG_EROFS_FS_ZIP
-EROFS_ATTR_RW_UI(sync_decompress, erofs_mount_opts);
+EROFS_ATTR_RW_UI(sync_decompress, erofs_sb_info);
EROFS_ATTR_FUNC(drop_caches, 0200);
#endif
#ifdef CONFIG_EROFS_FS_ZIP_ACCEL
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 3d31f7840ca0..f07f9db3b019 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -9,6 +9,7 @@
#include <linux/cpuhotplug.h>
#include <trace/events/erofs.h>
+#define Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES 12288
#define Z_EROFS_PCLUSTER_MAX_PAGES (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
#define Z_EROFS_INLINE_BVECS 2
@@ -1095,21 +1096,6 @@ static int z_erofs_scan_folio(struct z_erofs_frontend *f,
return err;
}
-static bool z_erofs_is_sync_decompress(struct erofs_sb_info *sbi,
- unsigned int readahead_pages)
-{
- /* auto: enable for read_folio, disable for readahead */
- if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&
- !readahead_pages)
- return true;
-
- if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&
- (readahead_pages <= sbi->opt.max_sync_decompress_pages))
- return true;
-
- return false;
-}
-
static bool z_erofs_page_is_invalidated(struct page *page)
{
return !page_folio(page)->mapping && !z_erofs_is_shortlived_page(page);
@@ -1483,9 +1469,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
#else
queue_work(z_erofs_workqueue, &io->u.work);
#endif
- /* enable sync decompression for readahead */
- if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
- sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
+ /* See `sync_decompress` in sysfs-fs-erofs for more details */
+ if (sbi->sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
+ sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
return;
}
z_erofs_decompressqueue_work(&io->u.work);
@@ -1802,16 +1788,21 @@ static void z_erofs_submit_queue(struct z_erofs_frontend *f,
z_erofs_decompress_kickoff(q[JQ_SUBMIT], nr_bios);
}
-static int z_erofs_runqueue(struct z_erofs_frontend *f, unsigned int rapages)
+static int z_erofs_runqueue(struct z_erofs_frontend *f, unsigned int rabytes)
{
struct z_erofs_decompressqueue io[NR_JOBQUEUES];
struct erofs_sb_info *sbi = EROFS_I_SB(f->inode);
- bool force_fg = z_erofs_is_sync_decompress(sbi, rapages);
+ int syncmode = sbi->sync_decompress;
+ bool force_fg;
int err;
+ force_fg = (syncmode == EROFS_SYNC_DECOMPRESS_AUTO && !rabytes) ||
+ (syncmode == EROFS_SYNC_DECOMPRESS_FORCE_ON &&
+ (rabytes <= Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES));
+
if (f->head == Z_EROFS_PCLUSTER_TAIL)
return 0;
- z_erofs_submit_queue(f, io, &force_fg, !!rapages);
+ z_erofs_submit_queue(f, io, &force_fg, !!rabytes);
/* handle bypass queue (no i/o pclusters) immediately */
err = z_erofs_decompress_queue(&io[JQ_BYPASS], &f->pagepool);
@@ -1932,7 +1923,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
z_erofs_pcluster_readmore(&f, rac, false);
z_erofs_pcluster_end(&f);
- (void)z_erofs_runqueue(&f, nrpages);
+ (void)z_erofs_runqueue(&f, nrpages << PAGE_SHIFT);
erofs_put_metabuf(&f.map.buf);
erofs_release_pages(&f.pagepool);
}
--
2.43.5
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