[PATCH] erofs: avoid noisy messages for transient -ENOMEM

[Gao Xiang <hsiangkao@linux.alibaba.com>]

EROFS may allocate temporary pages using GFP_NOWAIT | GFP_NORETRY
when pcl->besteffort is off (e.g., for readahead requests).

If the allocation fails, the original request will fall back to
synchronous read, so the failure is transient.

Such fallback can frequently happen in low memory scenarios, but since
these failures are expected and temporary, avoid printing error
messages like below:

[ 7425.184264] erofs (device sr0): failed to decompress (lz4) -ENOMEM @ pa 148447232 size 28672 => 26788
[ 7426.244267] erofs (device sr0): failed to decompress (lz4) -ENOMEM @ pa 149422080 size 28672 => 15903
[ 7426.245508] erofs (device sr0): failed to decompress (lz4) -ENOMEM @ pa 138440704 size 28672 => 39294
...
[ 7504.258373] erofs (device sr0): failed to decompress (lz4) -ENOMEM @ pa 93581312 size 20480 => 47366

Fixes: 831faabed812 ("erofs: improve decompression error reporting")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/zdata.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 3d31f7840ca0..bc2e0d3b97dd 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1324,9 +1324,10 @@ static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, bool eio)
 						GFP_NOWAIT | __GFP_NORETRY
 				 }, be->pagepool);
 		if (IS_ERR(reason)) {
-			erofs_err(be->sb, "failed to decompress (%s) %ld @ pa %llu size %u => %u",
-				  alg->name, PTR_ERR(reason), pcl->pos,
-				  pcl->pclustersize, pcl->length);
+			if (pcl->besteffort || reason != ERR_PTR(-ENOMEM))
+				erofs_err(be->sb, "failed to decompress (%s) %ld @ pa %llu size %u => %u",
+					  alg->name, PTR_ERR(reason), pcl->pos,
+					  pcl->pclustersize, pcl->length);
 			err = PTR_ERR(reason);
 		} else if (unlikely(reason)) {
 			erofs_err(be->sb, "failed to decompress (%s) %s @ pa %llu size %u => %u",
-- 
2.43.5