linux-stable.git/drivers/block/floppy.c, branch v5.7.4

block/floppy: fix contended case in floppy_queue_rq()

2020-06-17T14:43:04+00:00

commit 263c61581a38d0a5ad1f5f4a9143b27d68caeffd upstream.

Since the switch of floppy driver to blk-mq, the contended (fdc_busy) case
in floppy_queue_rq() is not handled correctly.

In case we reach floppy_queue_rq() with fdc_busy set (i.e. with the floppy
locked due to another request still being in-flight), we put the request
on the list of requests and return BLK_STS_OK to the block core, without
actually scheduling delayed work / doing further processing of the
request. This means that processing of this request is postponed until
another request comes and passess uncontended.

Which in some cases might actually never happen and we keep waiting
indefinitely. The simple testcase is

	for i in `seq 1 2000`; do echo -en $i '\r'; blkid --info /dev/fd0 2> /dev/null; done

run in quemu. That reliably causes blkid eventually indefinitely hanging
in __floppy_read_block_0() waiting for completion, as the BIO callback
never happens, and no further IO is ever submitted on the (non-existent)
floppy device. This was observed reliably on qemu-emulated device.

Fix that by not queuing the request in the contended case, and return
BLK_STS_RESOURCE instead, so that blk core handles the request
rescheduling and let it pass properly non-contended later.

Fixes: a9f38e1dec107a ("floppy: convert to blk-mq")
Cc: stable@vger.kernel.org
Tested-by: Libor Pechacek 
Signed-off-by: Jiri Kosina 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

floppy: rename the global "fdc" variable to "current_fdc"

2020-03-16T14:26:58+00:00

This is done in order to remove the confusion that arises at some places
in the code where local variables or arguments shadow the global variable.
It is already visible that some places are a bit awkward and iterate over
the global variable, for the sole reason that they used to rely on it being
named "fdc" in order to get the correct address when using FD_DOR. These
ones are easy to spot by searching for "for (current_fdc...".

Some more cleanup is definitely possible. For example
"fdc_state[current_fdc].somefield" is used all over the code and would
probably be better with "fdc_state->somefield" with fdc_state being set
when current_fdc is assigned. This would require to pass the pointer to
the current state instead of the current_fdc to the I/O functions.

Link: https://lore.kernel.org/r/20200301195555.11154-7-w@1wt.eu
Cc: Linus Torvalds 
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: separate the FDC's base address from its registers

2020-03-16T14:26:58+00:00

FDC registers FD_STATUS, FD_DATA, FD_DOR, FD_DIR and FD_DCR used to be
defined relative to FD_IOPORT, which is the FDC's base address, itself
a macro depending on the "fdc" local or global variable.

This patch changes this so that the register macros above now only
reference the address offset, and that the FDC's address is explicitly
passed in each call to fd_inb() and fd_outb(), thus removing the macro.
With this change there is no more implicit usage of the local/global
"fdc" variable.

One place in the ARM code used to check if the port was equal to FD_DOR,
this was changed to testing the register by applying a mask to the port,
as was already done in the sparc code.

There are still occurrences of fd_inb() and fd_outb() in the PARISC
code and these ones remain unaffected since they already used to work
with a base address and a register offset.

The sparc, m68k and parisc code could now be slightly cleaned up to
benefit from the macro definitions above instead of the equivalent
hard-coded values.

Link: https://lore.kernel.org/r/20200301195555.11154-6-w@1wt.eu
Cc: Ian Molton 
Cc: Russell King 
Cc: Linus Torvalds 
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: introduce new functions fdc_inb() and fdc_outb()

2020-03-16T14:26:58+00:00

These two functions replace fd_inb() and fd_outb() in that they take
the FDC in argument. This will ease the separation of the base address
and the port everywhere the code is used.

Link: https://lore.kernel.org/r/20200301195555.11154-5-w@1wt.eu
Cc: Linus Torvalds 
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand the reply_buffer macros

2020-03-16T14:26:58+00:00

Several macros were used to access reply_buffer[] at discrete positions
without making it obvious they were relying on this. These ones have
been replaced by their offset in the reply buffer to make these accesses
more obvious.

Link: https://lore.kernel.org/r/20200224212352.8640-11-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand the R/W / format command macros

2020-03-16T14:26:57+00:00

Various macros were used to access raw_cmd for R/W or format commands
without making it obvious that raw_cmd->cmd[] was used. Let's expand
the macros to make this more obvious.

Link: https://lore.kernel.org/r/20200224212352.8640-10-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand macro DRWE

2020-03-16T14:26:57+00:00

This macro doesn't bring much value and only slightly obfuscates the
code by silently using global variable "current_drive", let's expand it.

Link: https://lore.kernel.org/r/20200224212352.8640-9-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand macro DRS

2020-03-16T14:26:57+00:00

This macro doesn't bring much value and only slightly obfuscates the
code by silently using global variable "current_drive", let's expand it.

Link: https://lore.kernel.org/r/20200224212352.8640-8-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand macro DP

2020-03-16T14:26:57+00:00

This macro doesn't bring much value and only slightly obfuscates the
code by silently using global variable "current_drive", let's expand it.

Link: https://lore.kernel.org/r/20200224212352.8640-7-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe

floppy: cleanup: expand macro UDRWE

2020-03-16T14:26:57+00:00

This macro doesn't bring much value and only slightly obfuscates the
code by silently using local variable "drive", let's expand it.

Link: https://lore.kernel.org/r/20200224212352.8640-6-w@1wt.eu
Signed-off-by: Willy Tarreau 
Signed-off-by: Denis Efremov 
Signed-off-by: Jens Axboe