According to 'man 2 close' errors returned by close() should only be used
for either diagnostic purposes or for catching data loss due to a previous
write error, as an error result of close() usually indicates a deferred
error of a previous write operation.
Therefore not decrementing 'total_open_fd' on a close() error is wrong
and would yield in a higher open file descriptor count than actually the
case, leading to 9p server reclaiming open file descriptors too soon.
Based-on: <20250312152933.383967-7-gr...@kaod.org>
Signed-off-by: Christian Schoenebeck <qemu_...@crudebyte.com>
Reviewed-by: Greg Kurz <gr...@kaod.org>
Message-Id: <e1tveyj-004dma...@kylie.crudebyte.com>
---
hw/9pfs/9p.c | 10 +++++++++-
hw/9pfs/codir.c | 7 ++++++-
hw/9pfs/cofile.c | 7 ++++++-
3 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index b22df3aa2b..8b001b9112 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -510,7 +510,15 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
err = (f->fid_type == P9_FID_DIR) ?
s->ops->closedir(&s->ctx, &f->fs_reclaim) :
s->ops->close(&s->ctx, &f->fs_reclaim);
- if (!err) {
+
+ /* 'man 2 close' suggests to ignore close() errors except of EBADF
*/
+ if (unlikely(err && errno == EBADF)) {
+ /*
+ * unexpected case as FIDs were picked above by having a valid
+ * file descriptor
+ */
+ error_report("9pfs: v9fs_reclaim_fd() WARNING: close() failed
with EBADF");
+ } else {
/* total_open_fd must only be mutated on main thread */
nclosed++;
}
diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
index 2068a4779d..bce7dd96e9 100644
--- a/hw/9pfs/codir.c
+++ b/hw/9pfs/codir.c
@@ -20,6 +20,7 @@
#include "fsdev/qemu-fsdev.h"
#include "qemu/thread.h"
#include "qemu/main-loop.h"
+#include "qemu/error-report.h"
#include "coth.h"
#include "9p-xattr.h"
#include "9p-util.h"
@@ -353,7 +354,11 @@ int coroutine_fn v9fs_co_closedir(V9fsPDU *pdu,
V9fsFidOpenState *fs)
err = -errno;
}
});
- if (!err) {
+ /* 'man 2 close' suggests to ignore close() errors except of EBADF */
+ if (unlikely(err && errno == EBADF)) {
+ /* unexpected case as we should have checked for a valid file handle */
+ error_report("9pfs: WARNING: v9fs_co_closedir() failed with EBADF");
+ } else {
total_open_fd--;
}
return err;
diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c
index 71174c3e4a..6e775c8e41 100644
--- a/hw/9pfs/cofile.c
+++ b/hw/9pfs/cofile.c
@@ -20,6 +20,7 @@
#include "fsdev/qemu-fsdev.h"
#include "qemu/thread.h"
#include "qemu/main-loop.h"
+#include "qemu/error-report.h"
#include "coth.h"
int coroutine_fn v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, mode_t st_mode,
@@ -197,7 +198,11 @@ int coroutine_fn v9fs_co_close(V9fsPDU *pdu,
V9fsFidOpenState *fs)
err = -errno;
}
});
- if (!err) {
+ /* 'man 2 close' suggests to ignore close() errors except of EBADF */
+ if (unlikely(err && errno == EBADF)) {
+ /* unexpected case as we should have checked for a valid file handle */
+ error_report("9pfs: WARNING: v9fs_co_close() failed with EBADF");
+ } else {
total_open_fd--;
}
return err;
--
2.30.2
